Record build profile and temporal raster cost in lighting benchmark

cmake/Renderer.cmake

@@ -40,13 +40,17 @@ add_custom_command(OUTPUT "${FASET_SHADER_DIRECTORY}/compatibility.spv"
           -o "${FASET_SHADER_DIRECTORY}/compatibility.spv"
   DEPENDS "${PROJECT_SOURCE_DIR}/shaders/compatibility.hlsl" VERBATIM)
 add_custom_target(faset_shaders DEPENDS ${FASET_SHADER_OUTPUTS} "${FASET_SHADER_DIRECTORY}/compatibility.spv")
-add_library(faset_render "${PROJECT_SOURCE_DIR}/src/render/renderer.cpp" "${PROJECT_SOURCE_DIR}/src/render/math.cpp" "${PROJECT_SOURCE_DIR}/src/render/render_graph.cpp" "${PROJECT_SOURCE_DIR}/src/render/shader_contract.cpp")
+add_library(faset_render "${PROJECT_SOURCE_DIR}/src/render/renderer.cpp" "${PROJECT_SOURCE_DIR}/src/render/math.cpp" "${PROJECT_SOURCE_DIR}/src/render/render_graph.cpp" "${PROJECT_SOURCE_DIR}/src/render/shader_contract.cpp" "${PROJECT_SOURCE_DIR}/src/render/lighting.cpp")
 target_include_directories(faset_render PUBLIC "${PROJECT_SOURCE_DIR}/include")
 target_compile_features(faset_render PUBLIC cxx_std_20)
 target_link_libraries(faset_render PRIVATE Vulkan::Vulkan SDL3::SDL3 faset_core)
 target_compile_definitions(faset_render PRIVATE FASET_SHADER_DIRECTORY="${FASET_SHADER_DIRECTORY}")
 add_dependencies(faset_render faset_shaders)
 if(BUILD_TESTING)
+  add_executable(faset_render_lighting_policy_tests "${PROJECT_SOURCE_DIR}/tests/render_lighting_policy_tests.cpp")
+  target_link_libraries(faset_render_lighting_policy_tests PRIVATE faset_render)
+  add_test(NAME render_lighting_policy COMMAND faset_render_lighting_policy_tests)
+  set_tests_properties(render_lighting_policy PROPERTIES LABELS "p3")
   add_executable(faset_render_tests "${PROJECT_SOURCE_DIR}/tests/render_tests.cpp")
   target_link_libraries(faset_render_tests PRIVATE faset_render SDL3::SDL3)
   add_test(NAME render_graph COMMAND faset_render_tests --unit)
@@ -78,5 +82,17 @@ if(BUILD_TESTING)
   target_link_libraries(faset_render_window_tests PRIVATE faset_render SDL3::SDL3)
   add_test(NAME render_window_lifecycle COMMAND faset_render_window_tests "${CMAKE_BINARY_DIR}/window-test")
   set_tests_properties(render_window_lifecycle PROPERTIES LABELS "gpu;window" TIMEOUT 40 SKIP_RETURN_CODE 77)
+  add_executable(faset_p3_lighting_benchmark
+    "${PROJECT_SOURCE_DIR}/examples/renderer/p3_lighting_benchmark.cpp")
+  target_link_libraries(faset_p3_lighting_benchmark PRIVATE faset_render faset_core)
+  target_compile_definitions(faset_p3_lighting_benchmark PRIVATE
+    FASET_BENCHMARK_CONFIGURATION="$<CONFIG>")
+  add_test(NAME render_lighting_benchmark_schema COMMAND
+    "${Python3_EXECUTABLE}" "${PROJECT_SOURCE_DIR}/tests/test_p3_lighting_benchmark.py")
+  set_tests_properties(render_lighting_benchmark_schema PROPERTIES LABELS "p3" TIMEOUT 90)
+  add_test(NAME render_lighting_benchmark_smoke COMMAND
+    "${Python3_EXECUTABLE}" "${PROJECT_SOURCE_DIR}/tests/test_p3_lighting_benchmark.py"
+    --real-executable "$<TARGET_FILE:faset_p3_lighting_benchmark>")
+  set_tests_properties(render_lighting_benchmark_smoke PROPERTIES LABELS "gpu;p3" TIMEOUT 90)
 endif()
 install(FILES ${FASET_SHADER_OUTPUTS} DESTINATION shaders)

docs/manual/editor/lighting.md

@@ -0,0 +1,92 @@
+# Add lights to a 3D scene
+
+Add a **Light** component to a scene entity. The entity's transform places a point
+or spot light; its rotation aims a spot light along local negative Z. A directional
+light uses the entity's orientation. Light colors and intensity contribute to the
+mesh's linear PBR illumination before tone mapping. Sprites and UI retain their
+unlit tint.
+
+The version-1 `faset.light` component has three `kind` values:
+
+| Kind | Position and direction | Useful fields |
+| --- | --- | --- |
+| `directional` | Direction from the entity transform | `color`, `intensity`, `casts_shadow` |
+| `point` | Position from the entity transform; illuminates every direction | `color`, `intensity`, `range` |
+| `spot` | Position and local negative-Z direction | `color`, `intensity`, `range`, `inner_angle`, `outer_angle` |
+
+Angles are radians. A spot's inner angle must not exceed its outer angle. Intensity
+must be nonnegative and range positive. `enabled: false` keeps the component in the
+scene without contributing light. The `shadow_priority` integer is reserved for the
+bounded local-shadow scheduler; it does not change brightness.
+
+In the current rendering checkpoint, one enabled directional light can cast the
+existing single-map shadow. Point and spot lights illuminate meshes but do not yet
+cast shadows. The [P3 lighting plan](https://github.com/emil28092005/Faset_Engine/blob/main/docs/superpowers/plans/2026-09-24-p3-lighting.md)
+tracks cascades and the bounded local-shadow atlas. A scene with no Light component
+keeps the legacy white sun so older projects retain their appearance. Adding any
+Light component, even a disabled one, turns off that compatibility fallback. If
+several directionals are enabled, Faset chooses the one with the smallest stable
+entity ID and reports a diagnostic for the others.
+
+## Author a point light through MCP
+
+Use `faset_schema` to inspect the current field IDs, then send a `faset_scene_edit`
+batch with the document ID, current revision, and target entity ID. For example:
+
+```json
+{
+  "document": "REPLACE_WITH_DOCUMENT_ID",
+  "revision": 4,
+  "idempotency_key": "add-red-point-light",
+  "operations": [{
+    "op": "component.add",
+    "entity": "REPLACE_WITH_ENTITY_ID",
+    "type": "faset.light",
+    "fields": {
+      "kind": "point",
+      "color": [1, 0.15, 0.1, 1],
+      "intensity": 8,
+      "range": 6
+    }
+  }]
+}
+```
+
+Move the entity with its Transform component. `component.add` fills any omitted
+light fields from the version-1 schema; use `component.set` for later edits. See
+[MCP and command line](mcp.md) for revision and retry handling.
+
+## Supply lights directly from C++
+
+When building a `faset::render::Snapshot` yourself, set
+`authored_lights_present` to suppress the compatibility sun in a local-only scene.
+Provide a stable ID for each light so future shadow scheduling remains independent
+of submission order.
+
+```cpp
+faset::render::Snapshot snapshot;
+snapshot.authored_lights_present = true;
+
+faset::render::LocalLight point;
+point.kind = faset::render::LocalLight::Kind::Point;
+point.stable_id = "level/torch";
+point.position = {-2, 1.5f, 0};
+point.color = {1, 0.3f, 0.1f, 1};
+point.intensity = 8;
+point.range = 6;
+snapshot.local_lights.push_back(point);
+
+faset::render::LocalLight spot;
+spot.kind = faset::render::LocalLight::Kind::Spot;
+spot.stable_id = "level/lamp";
+spot.position = {2, 3, 0};
+spot.direction = {0, -1, 0};
+spot.inner_angle = 0.25f;
+spot.outer_angle = 0.55f;
+spot.intensity = 5;
+spot.range = 9;
+snapshot.local_lights.push_back(spot);
+```
+
+The renderer submits at most 128 local lights per frame in stable-ID order. Later
+P3 work adds explicit overflow diagnostics and measured light-list optimization.

docs/superpowers/plans/2026-09-24-p3-lighting.md

@@ -42,9 +42,9 @@ Tasks 1–3 define the shared interfaces. Integrate Task 2's descriptor ABI befo
 
 **Files:** Modify `include/faset/render/renderer.hpp`, `src/authoring/schema.cpp`, `src/player/SceneView.cpp`, `tests/authoring_tests.cpp`, `tests/runtime_player_tests.cpp`, and relevant Manual authoring examples.
 
-**Interfaces:** Introduce `SunLight { stable_id, direction, color, intensity, casts_shadow }`, `LocalLight { Kind::Point|Spot, stable_id, position, direction, color, intensity, range, inner_angle, outer_angle, casts_shadow, shadow_priority }`, and `CameraFrustum { view, projection, near_plane, far_plane, perspective }`. Add `std::optional<SunLight> Snapshot::sun`, `std::vector<LocalLight> Snapshot::local_lights`, and `std::optional<CameraFrustum> Snapshot::camera_frustum` after existing aggregate fields; retain `Snapshot::light_direction`. `SceneView::build` fills camera data for 3D scenes and picks the first enabled directional by stable ID.
+**Interfaces:** Introduce `SunLight { stable_id, direction, color, intensity, casts_shadow }`, `LocalLight { Kind::Point|Spot, stable_id, position, direction, color, intensity, range, inner_angle, outer_angle, casts_shadow, shadow_priority }`, and `CameraFrustum { view, projection, near_plane, far_plane, perspective }`. Add `std::optional<SunLight> Snapshot::sun`, `std::vector<LocalLight> Snapshot::local_lights`, `bool Snapshot::authored_lights_present` (default false), and `std::optional<CameraFrustum> Snapshot::camera_frustum` after existing aggregate fields; retain `Snapshot::light_direction`. `SceneView::build` fills camera data for 3D scenes, sets authored-light presence even for disabled/future-version light components, and picks the first enabled directional by stable ID. A legacy sun is synthesized only when both sun and authored-light presence are absent.
 
-- [ ] **Step 1: Write failing schema/extraction tests.** Construct a version-1 scene with directional, point, and spot entities in one order and reversed order. Assert all local IDs/properties agree; authored sun color/intensity are preserved; no-light scene retains the default legacy sun; extra directionals emit a diagnostic; invalid `range <= 0`, `inner_angle > outer_angle`, nonfinite color/transform, and unknown kind identify the entity/field. An essential assertion is:
+- [ ] **Step 1: Write failing schema/extraction tests.** Construct a version-1 scene with directional, point, and spot entities in one order and reversed order. Assert all local IDs/properties agree; authored sun color/intensity are preserved; a no-light scene has `authored_lights_present == false` and retains the default legacy sun, while a local-only or explicitly disabled-sun scene has the flag true and no sun. Extra directionals emit a diagnostic; invalid `range <= 0`, `inner_angle > outer_angle`, nonfinite color/transform, and unknown kind identify the entity/field. An essential assertion is:
   ```cpp
   auto a = view.build(scene_with_three_lights(), 16.f / 9.f);
   auto b = view.build(reordered_scene_with_three_lights(), 16.f / 9.f);
@@ -54,14 +54,14 @@ Tasks 1–3 define the shared interfaces. Integrate Task 2's descriptor ABI befo
         "Light ordering follows stable IDs, not entity array order");
   ```
 - [ ] **Step 2: Run the focused tests red.** Run `cmake --preset linux-debug` and `cmake --build --preset linux-debug --target faset_authoring_tests faset_player_tests --parallel 4`; missing typed fields should fail compilation. If compilation succeeds, `ctest --test-dir build/linux-debug --output-on-failure --no-tests=error -R '^(authoring|player_scene_contracts)$'` must fail on a new behavioral assertion. Record the expected failure rather than assuming the build itself must be red.
-- [ ] **Step 3: Add schema defaults and extraction.** Keep builtin version 1; use `fields.value` for additive fields, normalize directions after the world transform, validate finite/color/range/cone values, sort by stable ID, and preserve the legacy fallback. Set `camera_frustum` from the same unjittered view/projection used to form `view_projection`. Update direct C++ API examples to construct one point and one spot light.
+- [ ] **Step 3: Add schema defaults and extraction.** Keep builtin version 1; use `fields.value` for additive fields, normalize directions after the world transform, validate finite/color/range/cone values, sort by stable ID, and preserve the legacy fallback only when no authored light component exists. Set `camera_frustum` from the same unjittered view/projection used to form `view_projection`. Update direct C++ API examples to construct one point and one spot light.
   ```cpp
   struct CameraFrustum {
       Mat4 view{identity}, projection{identity};
       float near_plane{0.1f}, far_plane{1000.f};
       bool perspective{true};
   };
-  // Snapshot::light_direction remains available to callers without Snapshot::sun.
+  // Snapshot::light_direction remains a fallback only if authored_lights_present is false.
   ```
 - [ ] **Step 4: Run focused tests green.** `ctest --test-dir build/linux-debug --output-on-failure -R '^(authoring|player_scene_contracts)$'` passes, including old version-1 scenes and exported-scene decoding.
 - [ ] **Step 5: Commit** `Expose authored sun, point, and spot lights in render snapshots`.

docs/superpowers/specs/2026-09-24-p3-lighting-design.md

@@ -12,7 +12,7 @@ P3 supplies one sun plus point and spot lights, camera-fitted cascaded sun shado
 
 Keep `faset.light` at builtin schema version 1 and add optional fields with defaults: `kind` (`directional`, `point`, `spot`, default `directional`), `enabled` (true), `color` (white), `intensity` (1, nonnegative), `range` (10, positive, for local lights), `inner_angle` (0.35 radians), `outer_angle` (0.70 radians, strictly below π/2), `casts_shadow` (true), and `shadow_priority` (integer 0). Existing fields and component IDs remain valid. Cross-field validation requires `0 <= inner_angle <= outer_angle`; local range, color channels, intensity, transforms, and cone directions must be finite. Invalid authored values return a diagnostic with entity and field rather than nonfinite GPU data. Missing new fields use the schema defaults.
 
-`Snapshot` retains `light_direction` for existing direct-render clients. Add an optional `SunLight`, a vector of `LocalLight`, and an optional explicit `CameraFrustum` containing unjittered view/projection matrices, near/far distances, and projection kind. `SceneView` populates these from the authoring scene. Each light carries the stable entity/component identity, transformed position or normalized direction, color, intensity, range, cone angles, and shadow options. The first enabled directional light by stable ID is the sun; extra directionals produce a visible diagnostic until a later multi-sun design exists. If there is no authored directional light, the renderer synthesizes the legacy sun from `Snapshot::light_direction`. Local lights are ordered by stable ID to prevent reordering from changing atlas allocation or results. Point attenuation tends smoothly to zero at `range`; a spot multiplies it by a smooth inner-to-outer cone factor. The shader handles zero distance and invalid normals without NaN output.
+`Snapshot` retains `light_direction` for existing direct-render clients. Add an optional `SunLight`, a vector of `LocalLight`, an `authored_lights_present` flag (default false), and an optional explicit `CameraFrustum` containing unjittered view/projection matrices, near/far distances, and projection kind. `SceneView` populates these from the authoring scene and sets the flag if any authored light component exists, including a disabled or future-version component. Each light carries the stable entity/component identity, transformed position or normalized direction, color, intensity, range, cone angles, and shadow options. The first enabled directional light by stable ID is the sun; extra directionals produce a visible diagnostic until a later multi-sun design exists. The renderer synthesizes the legacy sun from `Snapshot::light_direction` only when `sun` is absent **and** `authored_lights_present` is false. Thus an old scene without light components keeps its previous appearance, while a local-only scene or explicitly disabled sun does not receive an unintended directional light. Low-level callers may set the flag to request a dark scene without authoring metadata. Local lights are ordered by stable ID to prevent reordering from changing atlas allocation or results. Point attenuation tends smoothly to zero at `range`; a spot multiplies it by a smooth inner-to-outer cone factor. The shader handles zero distance and invalid normals without NaN output.
 
 Explicit camera frustum data is required for four cascades. If a low-level caller supplies only the legacy `view_projection`, the renderer uses one bounded legacy-compatible sun shadow view and reports `effective_sun_cascades = 1`; it never silently claims CSM. 2D sprite-only snapshots do not incur shadow work. The future temporal stage may jitter the main raster projection, but the shadow planner consumes the unjittered `CameraFrustum` exclusively.
 

examples/renderer/p3_lighting_benchmark.cpp

@@ -0,0 +1,233 @@
+#include <faset/core/io.hpp>
+#include <faset/render/renderer.hpp>
+
+#include <algorithm>
+#include <array>
+#include <cstdint>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <iomanip>
+#include <iostream>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+
+using namespace faset::render;
+namespace fs = std::filesystem;
+
+namespace {
+struct Options {
+    unsigned lights{}, width{1920}, height{1080}, warmup{10}, frames{30}, run_index{};
+    bool shadows{}, validation{};
+    VisibilityMode visibility{VisibilityMode::Direct};
+    std::string commit{"unknown"}, driver{"unknown"};
+    fs::path csv, capture;
+};
+
+unsigned number(std::string_view text, std::string_view name) {
+    std::size_t end{};
+    const auto value = std::stoul(std::string(text), &end);
+    if (end != text.size() || value > 100000)
+        throw std::invalid_argument("Invalid value for " + std::string(name));
+    return static_cast<unsigned>(value);
+}
+
+Options parse(int argc, char** argv) {
+    Options options;
+    for (int i = 1; i < argc; ++i) {
+        const std::string name = argv[i];
+        if (name == "--list-runs") {
+            std::cout << "{\"lights\":[0,4,16,32,64,128],"
+                         "\"visibility\":[\"direct\",\"gpu-frustum\",\"gpu-occlusion\"],"
+                         "\"shadows\":[\"off\",\"on\"]}\n";
+            std::exit(0);
+        }
+        if (name == "--help") {
+            std::cout << "Usage: faset_p3_lighting_benchmark --lights 0|4|16|32|64|128 "
+                         "--shadows on|off --visibility direct|gpu-frustum|gpu-occlusion "
+                         "--csv PATH [--width N --height N --warmup N --frames N "
+                         "--run-index N --commit SHA --driver NAME --validation on|off "
+                         "--capture PATH]\n";
+            std::exit(0);
+        }
+        if (i + 1 >= argc)
+            throw std::invalid_argument("Missing value for " + name);
+        const std::string value = argv[++i];
+        if (name == "--lights") options.lights = number(value, name);
+        else if (name == "--width") options.width = number(value, name);
+        else if (name == "--height") options.height = number(value, name);
+        else if (name == "--warmup") options.warmup = number(value, name);
+        else if (name == "--frames") options.frames = number(value, name);
+        else if (name == "--run-index") options.run_index = number(value, name);
+        else if (name == "--commit") options.commit = value;
+        else if (name == "--driver") options.driver = value;
+        else if (name == "--csv") options.csv = faset::path_from_utf8(value);
+        else if (name == "--capture") options.capture = faset::path_from_utf8(value);
+        else if (name == "--shadows") {
+            if (value != "on" && value != "off")
+                throw std::invalid_argument("--shadows must be on or off");
+            options.shadows = value == "on";
+        } else if (name == "--validation") {
+            if (value != "on" && value != "off")
+                throw std::invalid_argument("--validation must be on or off");
+            options.validation = value == "on";
+        } else if (name == "--visibility") {
+            if (value == "direct") options.visibility = VisibilityMode::Direct;
+            else if (value == "gpu-frustum") options.visibility = VisibilityMode::GpuFrustum;
+            else if (value == "gpu-occlusion") options.visibility = VisibilityMode::GpuOcclusion;
+            else throw std::invalid_argument("Unknown visibility mode: " + value);
+        } else throw std::invalid_argument("Unknown option: " + name);
+    }
+    constexpr std::array allowed_lights{0u, 4u, 16u, 32u, 64u, 128u};
+    if (options.csv.empty() || options.width == 0 || options.height == 0 ||
+        options.frames == 0 || options.warmup > 1000 ||
+        std::find(allowed_lights.begin(), allowed_lights.end(), options.lights) ==
+            allowed_lights.end())
+        throw std::invalid_argument("Invalid benchmark configuration");
+    return options;
+}
+
+const char* mode_name(VisibilityMode mode) {
+    switch (mode) {
+    case VisibilityMode::Direct: return "direct";
+    case VisibilityMode::GpuFrustum: return "gpu-frustum";
+    case VisibilityMode::GpuOcclusion: return "gpu-occlusion";
+    }
+    return "unknown";
+}
+
+void csv_text(std::ostream& out, std::string_view value) {
+    out << '"';
+    for (const char c : value) {
+        if (c == '"') out << '"';
+        out << c;
+    }
+    out << '"';
+}
+
+Snapshot benchmark_scene(const Options& options) {
+    Snapshot scene;
+    scene.view_id = "p3-lighting-benchmark-fixed-scene";
+    scene.eye = {0, 0, 9};
+    scene.projection = perspective(.9f, float(options.width) / float(options.height), .1f, 100);
+    const auto view = look_at(scene.eye, {0, 0, 0});
+    scene.view_projection = multiply(scene.projection, view);
+    scene.camera_frustum = CameraFrustum{view, scene.projection, .1f, 100, true};
+    scene.authored_lights_present = true;
+    scene.clear_color = {.035f, .04f, .05f, 1};
+    DrawItem receiver;
+    receiver.mesh = cube_mesh();
+    receiver.model = transform({0, 0, -.15f}, {}, {10, 7.5f, .2f});
+    receiver.color = {.65f, .67f, .7f, 1};
+    receiver.roughness = .65f;
+    receiver.cast_shadow = options.shadows;
+    receiver.instance_key = "large-receiver";
+    scene.draws.push_back(receiver);
+    for (int i = 0; i < 9; ++i) {
+        DrawItem object;
+        object.mesh = cube_mesh();
+        object.model = transform({(float(i % 3) - 1.f) * 2.5f,
+                                  (float(i / 3) - 1.f) * 1.8f, .45f},
+                                 {}, {.42f, .42f, .6f});
+        object.color = {.6f + .1f * float(i % 3), .5f, .4f + .1f * float(i / 3), 1};
+        object.cast_shadow = options.shadows;
+        object.instance_key = "caster-" + std::to_string(i);
+        scene.draws.push_back(std::move(object));
+    }
+    for (unsigned i = 0; i < options.lights; ++i) {
+        LocalLight light;
+        light.kind = LocalLight::Kind::Point;
+        light.stable_id = "benchmark-light-" + std::to_string(i);
+        light.position = {(float(i % 8) - 3.5f) * 1.35f,
+                          (float((i / 8) % 8) - 3.5f) * .95f,
+                          2.f + .35f * float(i % 3)};
+        light.color = {.6f + .4f * float(i % 3 == 0),
+                       .6f + .4f * float(i % 3 == 1),
+                       .6f + .4f * float(i % 3 == 2), 1};
+        light.intensity = 5.f;
+        light.range = 8.f;
+        light.casts_shadow = options.shadows;
+        scene.local_lights.push_back(std::move(light));
+    }
+    return scene;
+}
+
+void benchmark(const Options& options) {
+    RendererConfig config;
+    config.width = options.width;
+    config.height = options.height;
+    config.headless = true;
+    config.validation = options.validation;
+    config.visibility_mode = options.visibility;
+    auto renderer = Renderer(config);
+    const auto scene = benchmark_scene(options);
+    for (unsigned i = 0; i < options.warmup; ++i)
+        renderer.render(scene);
+    if (!options.csv.parent_path().empty())
+        fs::create_directories(faset::native_io_path(options.csv.parent_path()));
+    std::ofstream csv(faset::native_io_path(options.csv));
+    if (!csv)
+        throw std::runtime_error("Cannot open benchmark CSV: " + faset::path_to_utf8(options.csv));
+    csv << "light_count,shadows,visibility,effective_visibility,lighting_path,"
+           "build_configuration,run_index,frame,"
+           "device,driver,commit,width,height,validation_enabled,validation_errors,"
+           "submitted_local_lights,omitted_local_lights,shadow_tiles,draw_calls,gpu_bytes,"
+           "gpu_main_raster_ms,gpu_post_raster_ms,gpu_post_visible,visibility_counters_valid,"
+           "gpu_shadow_ms,gpu_ms,cpu_ms,readback_cpu_ms\n";
+    csv << std::fixed << std::setprecision(6);
+    for (unsigned frame = 0; frame < options.frames; ++frame) {
+        renderer.render(scene);
+        const auto stats = renderer.stats();
+        if (stats.validation_errors != 0)
+            throw std::runtime_error("Vulkan validation error during benchmark");
+        if (stats.submitted_local_lights != options.lights || stats.omitted_local_lights != 0)
+            throw std::runtime_error("Renderer did not submit every requested local light");
+        if (stats.effective_visibility_mode != options.visibility)
+            throw std::runtime_error("Requested visibility path fell back during benchmark");
+        if (stats.gpu_main_raster_ms <= 0 || stats.gpu_ms <= 0)
+            throw std::runtime_error("GPU raster or frame timestamp was unavailable");
+        csv << options.lights << ',' << (options.shadows ? "on" : "off") << ','
+            << mode_name(options.visibility) << ',' << mode_name(stats.effective_visibility_mode)
+            << ",forward," << FASET_BENCHMARK_CONFIGURATION << ','
+            << options.run_index << ',' << frame << ',';
+        csv_text(csv, stats.device);
+        csv << ',';
+        csv_text(csv, options.driver);
+        csv << ',';
+        csv_text(csv, options.commit);
+        csv << ',' << options.width << ',' << options.height << ','
+            << (stats.validation_enabled ? 1 : 0) << ',' << stats.validation_errors << ','
+            << stats.submitted_local_lights << ',' << stats.omitted_local_lights
+            << ",0," << stats.draw_calls << ',' << stats.gpu_allocated_bytes << ','
+            << stats.gpu_main_raster_ms << ',' << stats.gpu_post_raster_ms << ','
+            << stats.gpu_post_visible << ',' << (stats.visibility_counters_valid ? 1 : 0)
+            << ",0," << stats.gpu_ms << ','
+            << stats.cpu_ms << ',' << stats.readback_cpu_ms << '\n';
+    }
+    if (!csv)
+        throw std::runtime_error("Cannot finish benchmark CSV: " + faset::path_to_utf8(options.csv));
+    if (!options.capture.empty())
+        renderer.capture(faset::native_io_path(options.capture));
+}
+} // namespace
+
+int benchmark_main(int argc, char** argv) {
+    try {
+        benchmark(parse(argc, argv));
+        return 0;
+    } catch (const std::exception& error) {
+        std::cerr << "P3 lighting benchmark: " << error.what() << '\n';
+        return 1;
+    }
+}
+
+#ifdef _WIN32
+int wmain(int argc, wchar_t** argv) {
+    return faset::run_utf8_main(argc, argv, benchmark_main);
+}
+#else
+int main(int argc, char** argv) {
+    return benchmark_main(argc, argv);
+}
+#endif

include/faset/render/lighting.hpp

@@ -0,0 +1,76 @@
+#pragma once
+#include <faset/render/visibility.hpp>
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <string>
+#include <vector>
+
+namespace faset::render {
+
+enum class ShadowDropReason { None, Unavailable, TileBudget, CasterBudget };
+enum class ShadowRedrawReason { EveryFrame };
+
+struct ShadowBudget {
+    std::uint32_t max_sun_views{4};
+    std::uint32_t max_local_faces{16};
+    std::uint32_t max_caster_draws{4096};
+    std::uint32_t max_local_lights{128};
+    std::uint32_t sun_atlas_size{2048};
+    std::uint32_t local_atlas_size{2048};
+    float max_shadow_distance{80};
+    bool sun_atlas_available{true};
+    bool local_atlas_available{true};
+};
+
+struct ShadowCasterBounds {
+    Bounds world;
+    std::uint32_t draw_index{}; // Index of the original source LOD-0 DrawItem.
+};
+
+struct ShadowView {
+    enum class Kind { Sun, Spot, Point };
+    Kind kind{Kind::Sun};
+    std::string light_id;
+    std::uint32_t face_index{};
+    std::uint32_t tile_index{};
+    std::uint32_t tile_origin_x{}, tile_origin_y{}, tile_size{}, usable_size{};
+    Mat4 view_projection{identity};
+    std::array<float, 4> atlas_scale_offset{};
+    std::array<float, 4> guarded_clamp{};
+    float split_near{}, split_far{};
+    float snapped_center_x{}, snapped_center_y{};
+    std::vector<std::uint32_t> caster_indices;
+    bool valid{};
+    ShadowDropReason reason{ShadowDropReason::None};
+    ShadowRedrawReason redraw_reason{ShadowRedrawReason::EveryFrame};
+};
+
+struct LocalShadowAssignment {
+    std::size_t source_index{};
+    std::uint32_t first_view{};
+    std::uint32_t face_count{};
+    bool valid{};
+    ShadowDropReason reason{ShadowDropReason::None};
+};
+
+struct ShadowPlan {
+    std::vector<ShadowView> sun_views; // Requested slots, including explicitly invalid ones.
+    std::vector<ShadowView> local_views; // Only complete, valid spot/point allocations.
+    std::vector<std::size_t> submitted_local_indices; // Priority/influence/stable-ID order.
+    std::vector<LocalShadowAssignment> local_assignments;
+    std::uint32_t requested_sun_cascades{}, effective_sun_cascades{};
+    std::uint32_t local_faces_requested{}, local_faces_used{};
+    std::uint32_t dropped_sun_views{}, dropped_local_faces{}, dropped_point_faces{};
+    std::uint32_t omitted_local_lights{}, caster_draws{};
+    std::uint32_t sun_atlas_size{}, local_atlas_size{};
+};
+
+// Stateless: every scheduled tile is cleared/redrawn; no prior-frame depth or
+// ownership is reused. Shadow casters are source LOD-0 world bounds, independent
+// of the camera/P2 visibility decision. This function performs no Vulkan work.
+ShadowPlan build_shadow_plan(const Snapshot& frame,
+                             std::span<const ShadowCasterBounds> casters,
+                             const ShadowBudget& budget = {});
+
+} // namespace faset::render

include/faset/render/renderer.hpp

@@ -80,6 +80,34 @@ struct Text {
     Color color{0.85f, 0.87f, 0.90f, 1};
     float size{14};
 };
+struct SunLight {
+    std::string stable_id;
+    Vec3 direction{-0.5f, -1, -0.3f};
+    Color color{1, 1, 1, 1};
+    float intensity{1};
+    bool casts_shadow{true};
+};
+struct LocalLight {
+    enum class Kind { Point, Spot };
+    Kind kind{Kind::Point};
+    std::string stable_id;
+    Vec3 position{};
+    Vec3 direction{0, 0, -1};
+    Color color{1, 1, 1, 1};
+    float intensity{1};
+    float range{10};
+    float inner_angle{0.35f};
+    float outer_angle{0.7f};
+    bool casts_shadow{true};
+    int shadow_priority{};
+};
+struct CameraFrustum {
+    Mat4 view{identity};
+    Mat4 projection{identity};
+    float near_plane{0.1f};
+    float far_plane{1000};
+    bool perspective{true};
+};
 struct Snapshot {
     // Optional scene viewport in drawable pixels (x, y, width, height); zero size uses the full
     // target.
@@ -100,6 +128,12 @@ struct Snapshot {
     // Distinguishes temporal histories when one Renderer displays different views.
     std::string view_id{};
     bool camera_cut{};
+    // Empty legacy scenes may use the renderer's compatibility sun. Any authored light
+    // component, including an explicitly disabled or opaque future one, suppresses it.
+    bool authored_lights_present{};
+    std::optional<SunLight> sun{};
+    std::vector<LocalLight> local_lights;
+    std::optional<CameraFrustum> camera_frustum{};
 };
 enum class VisibilityMode { Direct, GpuFrustum, GpuOcclusion };
 // CPU-only validation used before publishing a game or creating Vulkan pipelines.
@@ -149,6 +183,7 @@ struct FrameStats {
     std::uint64_t gpu_allocated_bytes{};
     std::uint32_t texture_count{};
     std::uint32_t vertices{}, draw_calls{}, culled_meshes{}, validation_errors{};
+    std::uint32_t submitted_local_lights{}, omitted_local_lights{};
     bool gpu_visibility_active{}, hzb_valid{};
     // Requested and actual paths for the last frame; actual may be less capable.
     VisibilityMode requested_visibility_mode{VisibilityMode::Direct};

mkdocs.yml

@@ -44,6 +44,7 @@ nav:
       - Editor workspace: editor/workspace.md
       - Scene templates: editor/templates.md
       - Assets and Blender: editor/assets.md
+      - Lighting: editor/lighting.md
       - GPU visibility and mesh LOD: editor/visibility-lod.md
       - Build, Play, and export: editor/export.md
       - Profiling and measurements: editor/profiling.md

shaders/baseline.slang

@@ -24,6 +24,32 @@ struct FrameParameters {
 [[vk::binding(1,0)]] SamplerState shadowSampler;
 [[vk::binding(2,0)]] Texture2D<float4> colorMap;
 [[vk::binding(3,0)]] SamplerState colorSampler;
+// Shared Direct/P2 graphics ABI. The legacy material set remains set 0;
+// GPU-only instance/visibility records occupy set 2.
+struct LightingHeader {
+    uint4 counts;                    // local count, sun enabled, sun shadow enabled, view count
+    float4 sunDirectionIntensity;    // xyz world-space ray direction, w intensity
+    float4 sunColor;
+    float4 cameraForwardShadowDistance;
+    float4 cascadeSplits;
+};
+struct LocalLightGpu {
+    float4 positionRange;
+    float4 directionCosOuter;
+    float4 colorIntensity;
+    float4 coneTypeShadowView;       // cos(inner), 0=point/1=spot, shadow view, flags
+    float4 reserved;
+};
+struct ShadowViewGpu {
+    column_major float4x4 viewProjection;
+    float4 tileScaleOffset;
+    float4 guardedClamp;
+    float4 biasFlags;
+};
+[[vk::binding(0,1)]] StructuredBuffer<LightingHeader> lightingFrame;
+[[vk::binding(1,1)]] StructuredBuffer<LocalLightGpu> localLights;
+[[vk::binding(2,1)]] StructuredBuffer<ShadowViewGpu> shadowViews;
+[[vk::binding(3,1)]] Texture2D<float> localShadowAtlas;
 [shader("vertex")]
 VertexOutput vertexMain(VertexInput v) {
     VertexOutput o;
@@ -32,6 +58,22 @@ VertexOutput vertexMain(VertexInput v) {
 }
 [shader("vertex")]
 float4 shadowMain(VertexInput v) : SV_Position { return mul(frame.lightViewProjection, float4(v.world,1)); }
+float3 directBRDF(float3 base, float rough, float metal, float3 n, float3 view, float3 l) {
+    const float pi = 3.14159265;
+    float nl = max(dot(n,l),0.0);
+    if (nl <= 0.0) return float3(0);
+    float3 halfVector = l + view;
+    float halfLengthSquared = dot(halfVector, halfVector);
+    float3 h = halfLengthSquared > 1e-8 ? halfVector * rsqrt(halfLengthSquared) : n;
+    float nv=max(dot(n,view),0.001), nh=max(dot(n,h),0.0), vh=max(dot(view,h),0.0);
+    float a=rough*rough, a2=a*a, denom=nh*nh*(a2-1.0)+1.0;
+    float d=a2/(pi*denom*denom+0.0001);
+    float k=(rough+1.0)*(rough+1.0)/8.0;
+    float g=(nl/(nl*(1.0-k)+k))*(nv/(nv*(1.0-k)+k));
+    float3 f0=lerp(float3(0.04),base,metal), fresnel=f0+(1.0-f0)*pow(1.0-vh,5.0);
+    float3 spec=d*g*fresnel/max(4.0*nv*nl,0.001);
+    return ((1.0-fresnel)*(1.0-metal)*base/pi+spec)*nl;
+}
 [shader("fragment")]
 float4 fragmentMain(VertexOutput v) : SV_Target {
     float4 sampled = colorMap.Sample(colorSampler, v.uv);
@@ -41,28 +83,52 @@ float4 fragmentMain(VertexOutput v) : SV_Target {
         return v.color * sampled;
     }
     float4 base = v.color * sampled;
-    const float pi = 3.14159265;
-    float3 n=normalize(v.normal), l=normalize(-frame.lightDirection.xyz), view=normalize(frame.eye.xyz-v.world), h=normalize(l+view);
-    float nl=max(dot(n,l),0.0), nv=max(dot(n,view),0.001), nh=max(dot(n,h),0.0), vh=max(dot(view,h),0.0);
+    LightingHeader lighting = lightingFrame[0];
+    float3 n=normalize(v.normal);
+    float3 viewDelta=frame.eye.xyz-v.world;
+    float viewLengthSquared=dot(viewDelta,viewDelta);
+    float3 view=viewLengthSquared > 1e-8 ? viewDelta*rsqrt(viewLengthSquared) : n;
     float rough=clamp(v.material.x,0.08,1.0), metal=saturate(v.material.y);
-    float a=rough*rough, a2=a*a, denom=nh*nh*(a2-1.0)+1.0;
-    float d=a2/(pi*denom*denom+0.0001);
-    float k=(rough+1.0)*(rough+1.0)/8.0;
-    float g=(nl/(nl*(1.0-k)+k))*(nv/(nv*(1.0-k)+k));
-    float3 f0=lerp(float3(0.04),base.rgb,metal), fresnel=f0+(1.0-f0)*pow(1.0-vh,5.0);
-    float3 spec=d*g*fresnel/max(4.0*nv*nl,0.001);
-    float4 lightClip=mul(frame.lightViewProjection,float4(v.world,1));
-    float3 projected=lightClip.xyz/lightClip.w;
-    float2 uv=projected.xy*.5+.5;
-    float visibility=1.0;
-    if(all(uv>=0.0)&&all(uv<=1.0)&&projected.z>=0.0&&projected.z<=1.0) {
-        visibility=0.0;
-        for(int y=-1;y<=1;++y) for(int x=-1;x<=1;++x) {
-            float depth=shadowMap.SampleLevel(shadowSampler,uv+float2(x,y)/1024.0,0);
-            visibility += projected.z-max(0.0008,0.003*(1.0-nl)) <= depth ? 1.0/9.0 : 0.0;
+    float3 linear=base.rgb*.12;
+    if (lighting.counts.y != 0 && lighting.sunDirectionIntensity.w > 0) {
+        float3 l=normalize(-lighting.sunDirectionIntensity.xyz);
+        float nl=max(dot(n,l),0.0);
+        float visibility=1.0;
+        if (lighting.counts.z != 0 && nl > 0) {
+            float4 lightClip=mul(frame.lightViewProjection,float4(v.world,1));
+            float3 projected=lightClip.xyz/lightClip.w;
+            float2 uv=projected.xy*.5+.5;
+            if(all(uv>=0.0)&&all(uv<=1.0)&&projected.z>=0.0&&projected.z<=1.0) {
+                visibility=0.0;
+                for(int y=-1;y<=1;++y) for(int x=-1;x<=1;++x) {
+                    float depth=shadowMap.SampleLevel(shadowSampler,uv+float2(x,y)/1024.0,0);
+                    visibility += projected.z-max(0.0008,0.003*(1.0-nl)) <= depth ? 1.0/9.0 : 0.0;
+                }
+            }
         }
+        linear += directBRDF(base.rgb, rough, metal, n, view, l) *
+                  lighting.sunColor.rgb * (lighting.sunDirectionIntensity.w * 3.0 * visibility);
+    }
+    for (uint i=0; i<lighting.counts.x; ++i) {
+        LocalLightGpu light=localLights[i];
+        float3 delta=light.positionRange.xyz-v.world;
+        float distanceSquared=max(dot(delta,delta),1e-6);
+        float distance=sqrt(distanceSquared);
+        float range=max(light.positionRange.w,1e-4);
+        if (distance >= range || light.colorIntensity.w <= 0) continue;
+        float3 l=delta/distance;
+        float relative=distance/range;
+        float cutoff=1.0-relative*relative*relative*relative;
+        float attenuation=cutoff*cutoff/(1.0+distanceSquared);
+        if (light.coneTypeShadowView.y > 0.5) {
+            float cosAngle=dot(-l,normalize(light.directionCosOuter.xyz));
+            float denominator=max(light.coneTypeShadowView.x-light.directionCosOuter.w,1e-4);
+            float cone=saturate((cosAngle-light.directionCosOuter.w)/denominator);
+            attenuation *= cone*cone*(3.0-2.0*cone);
+        }
+        linear += directBRDF(base.rgb, rough, metal, n, view, l) *
+                  light.colorIntensity.rgb * (light.colorIntensity.w * attenuation);
     }
-    float3 linear=base.rgb*.12 + ((1.0-fresnel)*(1.0-metal)*base.rgb/pi+spec)*nl*3.0*visibility;
     linear=linear/(1.0+linear);
     return float4(pow(max(linear,0),float3(1.0/2.2)),base.a);
 }

shaders/gpu_scene.slang

@@ -57,9 +57,9 @@ struct GpuFrameParameters {
     uint4 drawInfo; // x=visible ID range base; firstInstance is always zero
 };
 [[vk::push_constant]] ConstantBuffer<GpuFrameParameters> gpuFrame;
-[[vk::binding(0,1)]] StructuredBuffer<InstanceRecord> gfxInstances;
-[[vk::binding(1,1)]] StructuredBuffer<uint> gfxVisibleIds;
-[[vk::binding(2,1)]] StructuredBuffer<ViewRecord> gfxViews;
+[[vk::binding(0,2)]] StructuredBuffer<InstanceRecord> gfxInstances;
+[[vk::binding(1,2)]] StructuredBuffer<uint> gfxVisibleIds;
+[[vk::binding(2,2)]] StructuredBuffer<ViewRecord> gfxViews;
 
 // All indirect commands use firstInstance=0. The raw Vulkan index avoids the
 // BaseInstance read that Slang adds for SV_InstanceID (DrawParameters feature).

src/authoring/schema.cpp

@@ -156,6 +156,15 @@ void SchemaRegistry::validate_component(const Json& component) const {
     for (const auto& [id, value] : component["fields"].items())
         if (metadata["fields"].contains(id))
             validate_field(value, metadata["fields"][id]);
+    if (type == "faset.light") {
+        auto effective = default_fields(type);
+        effective.update(component.at("fields"));
+        if (effective.at("kind") == "spot")
+            require(effective.at("inner_angle").get<double>() <=
+                        effective.at("outer_angle").get<double>(),
+                    "validation.light_cone",
+                    "Spotlight inner_angle must not exceed outer_angle");
+    }
 }
 void SchemaRegistry::add_migration(const std::string& type, int from_version, Json rules) {
     require(contains(type) && from_version > 0 && from_version < schema(type).value("version", 1) &&
@@ -252,9 +261,25 @@ SchemaRegistry builtin_schemas() {
         {{"fov", Json{{"type", "number"}, {"default", 60.0}, {"min", 1.0}, {"max", 179.0}}},
          {"near", Json{{"type", "number"}, {"default", 0.1}, {"min", 0.001}}},
          {"far", Json{{"type", "number"}, {"default", 1000.0}, {"min", 0.01}}}});
-    add("faset.light", "Directional Light",
-        {{"color", field("color", {1, 1, 1, 1})},
-         {"intensity", Json{{"type", "number"}, {"default", 1.0}, {"min", 0.0}}}});
+    add("faset.light", "Light",
+        {{"kind", Json{{"type", "string"},
+                        {"default", "directional"},
+                        {"enum", {"directional", "point", "spot"}}}},
+         {"enabled", field("boolean", true)},
+         {"color", field("color", {1, 1, 1, 1})},
+         {"intensity", Json{{"type", "number"}, {"default", 1.0}, {"min", 0.0}}},
+         {"range", Json{{"type", "number"}, {"default", 10.0}, {"min", 0.001}}},
+         {"inner_angle", Json{{"type", "number"},
+                              {"default", 0.35}, {"min", 0.0}, {"max", 1.55},
+                              {"unit", "radians"}}},
+         {"outer_angle", Json{{"type", "number"},
+                              {"default", 0.7}, {"min", 0.001}, {"max", 1.55},
+                              {"unit", "radians"}}},
+         {"casts_shadow", field("boolean", true)},
+         {"shadow_priority", Json{{"type", "integer"},
+                                   {"default", 0},
+                                   {"min", std::numeric_limits<int>::min()},
+                                   {"max", std::numeric_limits<int>::max()}}}});
     for (int dimension : {2, 3}) {
         Json vector = dimension == 2 ? Json{0, 0} : Json{0, 0, 0};
         Json extents = dimension == 2 ? Json{0.5, 0.5} : Json{0.5, 0.5, 0.5};

src/player/SceneView.cpp

@@ -61,6 +61,16 @@ render::Vec3 direction(const render::Mat4& m, render::Vec3 p) {
     return {m[0] * p[0] + m[4] * p[1] + m[8] * p[2], m[1] * p[0] + m[5] * p[1] + m[9] * p[2],
             m[2] * p[0] + m[6] * p[1] + m[10] * p[2]};
 }
+render::Vec3 normalized(render::Vec3 value, const std::string& entityId,
+                        std::string_view field) {
+    const auto length = std::hypot(value[0], value[1], value[2]);
+    if (!std::isfinite(length) || length < 1e-6f)
+        throw std::invalid_argument("Light on entity " + entityId + " has invalid " +
+                                    std::string(field));
+    for (auto& axis : value)
+        axis /= length;
+    return value;
+}
 std::pair<std::string, std::string> reference(const std::string& ref) {
     const auto hash = ref.find('#');
     return {ref.substr(0, hash), hash == std::string::npos ? std::string{} : ref.substr(hash + 1)};
@@ -263,8 +273,12 @@ render::Snapshot SceneView::build(const Json& scene, float aspect, CameraSetting
         const auto id = entity.at("id").get<std::string>();
         if (!byId.emplace(id, &entity).second)
             throw std::invalid_argument("Duplicate scene ID");
+        if (!entity.contains("components") && entity.contains("light"))
+            out.authored_lights_present = true;
         for (const auto& component : entity.value("components", Json::array())) {
             const auto type = component.at("type").get<std::string>();
+            if (type == "faset.light")
+                out.authored_lights_present = true;
             if (component.value("version", 1) != 1 &&
                 (type == "faset.transform" || type == "faset.sprite" || type == "faset.mesh" ||
                  type == "faset.camera" || type == "faset.light"))
@@ -301,8 +315,15 @@ render::Snapshot SceneView::build(const Json& scene, float aspect, CameraSetting
     render::Vec3 cameraUp{0, 1, 0};
     bool foundCamera = false;
     std::vector<std::pair<int, render::Sprite>> sprites;
+    std::vector<render::SunLight> directionalLights;
     for (const auto& entity : entities) {
-        const auto model = world(world, entity);
+        const auto id = entity.at("id").get<std::string>();
+        render::Mat4 model;
+        try {
+            model = world(world, entity);
+        } catch (const std::exception& error) {
+            throw std::invalid_argument("Entity " + id + " transform: " + error.what());
+        }
         if (auto fields = properties(entity, "camera");
             !fields.is_null() && !camera.overrideSceneCamera && !foundCamera) {
             camera.eye = point(model, {0, 0, 0});
@@ -314,8 +335,97 @@ render::Snapshot SceneView::build(const Json& scene, float aspect, CameraSetting
             foundCamera = true;
             camera_id = entity.at("id").get<std::string>();
         }
-        if (auto fields = properties(entity, "light"); !fields.is_null())
-            out.light_direction = direction(model, {-0.5f, -1, -0.3f});
+        if (auto fields = properties(entity, "light"); !fields.is_null()) {
+            auto invalid = [&](std::string_view field) -> void {
+                throw std::invalid_argument("Light on entity " + id + " has invalid " +
+                                            std::string(field));
+            };
+            for (const auto entry : model)
+                if (!std::isfinite(entry))
+                    invalid("transform");
+            auto number = [&](const char* field, float fallback) {
+                if (!fields.contains(field))
+                    return fallback;
+                const auto& value = fields.at(field);
+                if (!value.is_number())
+                    invalid(field);
+                const auto decimal = value.get<double>();
+                if (!std::isfinite(decimal) ||
+                    std::abs(decimal) > std::numeric_limits<float>::max())
+                    invalid(field);
+                return static_cast<float>(decimal);
+            };
+            auto boolean = [&](const char* field, bool fallback) {
+                if (!fields.contains(field))
+                    return fallback;
+                if (!fields.at(field).is_boolean())
+                    invalid(field);
+                return fields.at(field).get<bool>();
+            };
+            const auto enabled = boolean("enabled", true);
+            if (enabled) {
+                if (fields.contains("kind") && !fields.at("kind").is_string())
+                    invalid("kind");
+                const auto kind = fields.value("kind", std::string("directional"));
+                if (kind != "directional" && kind != "point" && kind != "spot")
+                    invalid("kind");
+                render::Color color;
+                try {
+                    color = vec<4>(fields, "color", {1, 1, 1, 1});
+                } catch (const std::exception&) {
+                    invalid("color");
+                }
+                for (const auto channel : color)
+                    if (channel < 0)
+                        invalid("color");
+                const auto intensity = number("intensity", 1);
+                if (intensity < 0)
+                    invalid("intensity");
+                const auto castsShadow = boolean("casts_shadow", true);
+                const auto stableId = id;
+                if (kind == "directional") {
+                    directionalLights.push_back({stableId,
+                                                 normalized(direction(model, {-0.5f, -1, -0.3f}), id,
+                                                            "direction"),
+                                                 color, intensity, castsShadow});
+                } else {
+                    render::LocalLight local;
+                    local.kind = kind == "point" ? render::LocalLight::Kind::Point
+                                                 : render::LocalLight::Kind::Spot;
+                    local.stable_id = stableId;
+                    local.position = point(model, {0, 0, 0});
+                    for (const auto coordinate : local.position)
+                        if (!std::isfinite(coordinate))
+                            invalid("position");
+                    if (local.kind == render::LocalLight::Kind::Spot)
+                        local.direction = normalized(direction(model, {0, 0, -1}), id,
+                                                     "direction");
+                    local.color = color;
+                    local.intensity = intensity;
+                    local.range = number("range", 10);
+                    if (local.range <= 0)
+                        invalid("range");
+                    local.inner_angle = number("inner_angle", 0.35f);
+                    local.outer_angle = number("outer_angle", 0.7f);
+                    if (local.kind == render::LocalLight::Kind::Spot &&
+                        (local.inner_angle < 0 || local.inner_angle > local.outer_angle ||
+                         local.outer_angle <= 0 ||
+                         local.outer_angle >= std::numbers::pi_v<float> / 2))
+                        invalid("inner_angle/outer_angle");
+                    local.casts_shadow = castsShadow;
+                    if (fields.contains("shadow_priority")) {
+                        if (!fields.at("shadow_priority").is_number_integer())
+                            invalid("shadow_priority");
+                        const auto priority = fields.at("shadow_priority").get<double>();
+                        if (priority < std::numeric_limits<int>::min() ||
+                            priority > std::numeric_limits<int>::max())
+                            invalid("shadow_priority");
+                        local.shadow_priority = fields.at("shadow_priority").get<int>();
+                    }
+                    out.local_lights.push_back(std::move(local));
+                }
+            }
+        }
         if (auto fields = properties(entity, "sprite"); !fields.is_null()) {
             render::Sprite sprite;
             sprite.layer = fields.value("layer", 0);
@@ -372,6 +482,18 @@ render::Snapshot SceneView::build(const Json& scene, float aspect, CameraSetting
                      [](const auto& a, const auto& b) { return a.first < b.first; });
     for (auto& pair : sprites)
         out.sprites.push_back(std::move(pair.second));
+    std::sort(directionalLights.begin(), directionalLights.end(),
+              [](const auto& a, const auto& b) { return a.stable_id < b.stable_id; });
+    std::sort(out.local_lights.begin(), out.local_lights.end(),
+              [](const auto& a, const auto& b) { return a.stable_id < b.stable_id; });
+    if (!directionalLights.empty()) {
+        out.sun = directionalLights.front();
+        out.light_direction = out.sun->direction;
+        if (directionalLights.size() > 1)
+            impl_->messages.push_back("warning: multiple enabled directional lights; using " +
+                                      out.sun->stable_id + " and ignoring " +
+                                      std::to_string(directionalLights.size() - 1) + " others");
+    }
     if (dimension == 2) {
         const float height = camera.orthographicHeight;
         if (!std::isfinite(height) || height <= 0)
@@ -408,8 +530,10 @@ render::Snapshot SceneView::build(const Json& scene, float aspect, CameraSetting
         out.projection = render::perspective(
             camera.verticalFovDegrees * std::numbers::pi_v<float> / 180, aspect,
             camera.nearPlane, camera.farPlane);
-        out.view_projection = render::multiply(
-            out.projection, render::look_at(camera.eye, camera.target, cameraUp));
+        const auto view = render::look_at(camera.eye, camera.target, cameraUp);
+        out.view_projection = render::multiply(out.projection, view);
+        out.camera_frustum = render::CameraFrustum{view, out.projection, camera.nearPlane,
+                                                   camera.farPlane, true};
     }
     std::sort(impl_->messages.begin(), impl_->messages.end());
     impl_->messages.erase(std::unique(impl_->messages.begin(), impl_->messages.end()),

src/render/lighting.cpp

@@ -0,0 +1,392 @@
+#include <faset/render/lighting.hpp>
+#include <algorithm>
+#include <array>
+#include <cmath>
+#include <limits>
+#include <numbers>
+#include <stdexcept>
+#include <unordered_set>
+
+namespace faset::render {
+namespace {
+Vec3 add(Vec3 a, Vec3 b) { return {a[0] + b[0], a[1] + b[1], a[2] + b[2]}; }
+Vec3 subtract(Vec3 a, Vec3 b) { return {a[0] - b[0], a[1] - b[1], a[2] - b[2]}; }
+Vec3 scale(Vec3 a, float factor) { return {a[0] * factor, a[1] * factor, a[2] * factor}; }
+float dot(Vec3 a, Vec3 b) { return a[0] * b[0] + a[1] * b[1] + a[2] * b[2]; }
+float length(Vec3 a) { return std::sqrt(dot(a, a)); }
+Vec3 unit(Vec3 a) {
+    const float magnitude = length(a);
+    if (!std::isfinite(magnitude) || magnitude < 1e-6f)
+        throw std::invalid_argument("Shadow light direction must be finite and nonzero");
+    return scale(a, 1.f / magnitude);
+}
+Vec3 project(const Mat4& matrix, Vec3 value) {
+    return {matrix[0] * value[0] + matrix[4] * value[1] + matrix[8] * value[2] + matrix[12],
+            matrix[1] * value[0] + matrix[5] * value[1] + matrix[9] * value[2] + matrix[13],
+            matrix[2] * value[0] + matrix[6] * value[1] + matrix[10] * value[2] + matrix[14]};
+}
+std::array<float, 4> clip(const Mat4& matrix, Vec3 value) {
+    return {matrix[0] * value[0] + matrix[4] * value[1] + matrix[8] * value[2] + matrix[12],
+            matrix[1] * value[0] + matrix[5] * value[1] + matrix[9] * value[2] + matrix[13],
+            matrix[2] * value[0] + matrix[6] * value[1] + matrix[10] * value[2] + matrix[14],
+            matrix[3] * value[0] + matrix[7] * value[1] + matrix[11] * value[2] + matrix[15]};
+}
+std::array<Vec3, 8> corners(const Bounds& bounds) {
+    std::array<Vec3, 8> result{};
+    for (unsigned i = 0; i < 8; ++i)
+        result[i] = {i & 1 ? bounds.max[0] : bounds.min[0],
+                     i & 2 ? bounds.max[1] : bounds.min[1],
+                     i & 4 ? bounds.max[2] : bounds.min[2]};
+    return result;
+}
+Vec3 camera_to_world(const Mat4& view, Vec3 camera) {
+    // CameraFrustum::view is an unscaled, orthonormal look_at matrix.
+    return {view[0] * (camera[0] - view[12]) + view[1] * (camera[1] - view[13]) +
+                view[2] * (camera[2] - view[14]),
+            view[4] * (camera[0] - view[12]) + view[5] * (camera[1] - view[13]) +
+                view[6] * (camera[2] - view[14]),
+            view[8] * (camera[0] - view[12]) + view[9] * (camera[1] - view[13]) +
+                view[10] * (camera[2] - view[14])};
+}
+std::array<Vec3, 8> frustum_slice(const CameraFrustum& camera, float near_distance,
+                                  float far_distance) {
+    std::array<Vec3, 8> result{};
+    for (unsigned i = 0; i < 8; ++i) {
+        const float distance = i & 4 ? far_distance : near_distance;
+        const float x = i & 1 ? 1.f : -1.f;
+        const float y = i & 2 ? 1.f : -1.f;
+        Vec3 local{};
+        if (camera.perspective)
+            local = {x * distance / camera.projection[0],
+                     y * distance / camera.projection[5], -distance};
+        else
+            local = {(x - camera.projection[12]) / camera.projection[0],
+                     (y - camera.projection[13]) / camera.projection[5], -distance};
+        result[i] = camera_to_world(camera.view, local);
+    }
+    return result;
+}
+bool overlaps_xy(const Bounds& bounds, const Mat4& light_view, float left, float right,
+                 float bottom, float top) {
+    float min_x = std::numeric_limits<float>::infinity();
+    float max_x = -min_x, min_y = min_x, max_y = -min_x;
+    for (const auto point : corners(bounds)) {
+        const auto light = project(light_view, point);
+        min_x = std::min(min_x, light[0]);
+        max_x = std::max(max_x, light[0]);
+        min_y = std::min(min_y, light[1]);
+        max_y = std::max(max_y, light[1]);
+    }
+    return max_x >= left && min_x <= right && max_y >= bottom && min_y <= top;
+}
+bool intersects_frustum(const Bounds& bounds, const Mat4& view_projection) {
+    std::array<unsigned, 7> rejected{};
+    for (const auto point : corners(bounds)) {
+        const auto p = clip(view_projection, point);
+        if (!std::all_of(p.begin(), p.end(), [](float value) { return std::isfinite(value); }))
+            return true; // Invalid projection fails open so no caster is lost silently.
+        rejected[0] += p[0] < -p[3];
+        rejected[1] += p[0] > p[3];
+        rejected[2] += p[1] < -p[3];
+        rejected[3] += p[1] > p[3];
+        rejected[4] += p[2] < 0;
+        rejected[5] += p[2] > p[3];
+        rejected[6] += p[3] <= 0;
+    }
+    return std::none_of(rejected.begin(), rejected.end(), [](unsigned count) { return count == 8; });
+}
+void tile(ShadowView& view, std::uint32_t atlas_size, std::uint32_t tiles_across,
+          std::uint32_t index) {
+    constexpr std::uint32_t guard = 2;
+    const auto size = atlas_size / tiles_across;
+    view.tile_index = index;
+    view.tile_origin_x = (index % tiles_across) * size;
+    view.tile_origin_y = (index / tiles_across) * size;
+    view.tile_size = size;
+    view.usable_size = size - 2 * guard;
+    const auto reciprocal = 1.f / float(atlas_size);
+    view.atlas_scale_offset = {float(view.usable_size) * reciprocal,
+                               float(view.usable_size) * reciprocal,
+                               float(view.tile_origin_x + guard) * reciprocal,
+                               float(view.tile_origin_y + guard) * reciprocal};
+    view.guarded_clamp = {(float(view.tile_origin_x + guard) + 1.5f) * reciprocal,
+                          (float(view.tile_origin_y + guard) + 1.5f) * reciprocal,
+                          (float(view.tile_origin_x + size - guard) - 1.5f) * reciprocal,
+                          (float(view.tile_origin_y + size - guard) - 1.5f) * reciprocal};
+}
+std::vector<std::uint32_t> visible_casters(const Mat4& view_projection,
+                                           std::span<const ShadowCasterBounds> casters) {
+    std::vector<std::uint32_t> result;
+    for (const auto& caster : casters)
+        if (intersects_frustum(caster.world, view_projection))
+            result.push_back(caster.draw_index);
+    std::sort(result.begin(), result.end());
+    result.erase(std::unique(result.begin(), result.end()), result.end());
+    return result;
+}
+bool supported_atlas(std::uint32_t size, bool available) {
+    return available && (size == 2048 || size == 1024);
+}
+void validate_local(const LocalLight& light) {
+    const auto invalid = [&](const char* field) {
+        throw std::invalid_argument("Local light " + light.stable_id + " has invalid " + field);
+    };
+    if (light.stable_id.empty())
+        invalid("stable_id");
+    if (!std::all_of(light.position.begin(), light.position.end(),
+                     [](float v) { return std::isfinite(v); }))
+        invalid("position");
+    if (!std::all_of(light.color.begin(), light.color.end(),
+                     [](float v) { return std::isfinite(v) && v >= 0; }))
+        invalid("color");
+    if (!std::isfinite(light.intensity) || light.intensity < 0)
+        invalid("intensity");
+    if (!std::isfinite(light.range) || light.range <= 0)
+        invalid("range");
+    if (light.kind == LocalLight::Kind::Spot) {
+        if (!std::isfinite(light.inner_angle) || !std::isfinite(light.outer_angle) ||
+            light.inner_angle < 0 || light.inner_angle > light.outer_angle ||
+            light.outer_angle >= std::numbers::pi_v<float> / 2 || light.outer_angle <= 0)
+            invalid("inner_angle/outer_angle");
+        if (!std::all_of(light.direction.begin(), light.direction.end(),
+                         [](float v) { return std::isfinite(v); }) ||
+            length(light.direction) < 1e-6f)
+            invalid("direction");
+    }
+}
+float projected_influence(const LocalLight& light, const Snapshot& frame) {
+    const auto distance = length(subtract(light.position, frame.eye));
+    const auto projection_scale =
+        std::max(std::abs(frame.projection[0]), std::abs(frame.projection[5]));
+    return light.range * projection_scale / std::max(distance, .1f);
+}
+ShadowView sun_view(const Snapshot& frame, const SunLight& sun,
+                    std::span<const ShadowCasterBounds> casters, float split_near,
+                    float split_far, std::uint32_t index, std::uint32_t atlas_size) {
+    ShadowView result;
+    result.kind = ShadowView::Kind::Sun;
+    result.light_id = sun.stable_id;
+    result.face_index = index;
+    result.split_near = split_near;
+    result.split_far = split_far;
+    tile(result, atlas_size, 2, index);
+    const auto direction = unit(sun.direction);
+    const auto up = std::abs(direction[1]) > .98f ? Vec3{0, 0, 1} : Vec3{0, 1, 0};
+    const auto light_origin_view = look_at({0, 0, 0}, direction, up);
+    if (!frame.camera_frustum) {
+        const auto light_eye = scale(direction, -30);
+        result.view_projection = multiply(orthographic(-20, 20, -20, 20, .1f, 80),
+                                          look_at(light_eye, {0, 0, 0}, up));
+        result.caster_indices = visible_casters(result.view_projection, casters);
+        return result;
+    }
+    const auto receivers = frustum_slice(*frame.camera_frustum, split_near, split_far);
+    Vec3 center{};
+    for (const auto corner : receivers)
+        center = add(center, scale(corner, 1.f / 8));
+    float radius{};
+    for (const auto corner : receivers)
+        radius = std::max(radius, length(subtract(corner, center)));
+    radius = std::max(.25f, std::ceil(radius * 16.f) / 16.f);
+    const auto center_light = project(light_origin_view, center);
+    const auto texel = (2 * radius) / float(result.usable_size);
+    result.snapped_center_x = std::round(center_light[0] / texel) * texel;
+    result.snapped_center_y = std::round(center_light[1] / texel) * texel;
+    const float left = result.snapped_center_x - radius;
+    const float right = result.snapped_center_x + radius;
+    const float bottom = result.snapped_center_y - radius;
+    const float top = result.snapped_center_y + radius;
+    float nearest_ray = std::numeric_limits<float>::infinity();
+    float furthest_ray = -nearest_ray;
+    for (const auto corner : receivers) {
+        const auto ray = dot(corner, direction);
+        nearest_ray = std::min(nearest_ray, ray);
+        furthest_ray = std::max(furthest_ray, ray);
+    }
+    for (const auto& caster : casters) {
+        if (!overlaps_xy(caster.world, light_origin_view, left, right, bottom, top))
+            continue;
+        result.caster_indices.push_back(caster.draw_index);
+        for (const auto corner : corners(caster.world)) {
+            const auto ray = dot(corner, direction);
+            nearest_ray = std::min(nearest_ray, ray);
+            furthest_ray = std::max(furthest_ray, ray);
+        }
+    }
+    std::sort(result.caster_indices.begin(), result.caster_indices.end());
+    result.caster_indices.erase(
+        std::unique(result.caster_indices.begin(), result.caster_indices.end()),
+        result.caster_indices.end());
+    const auto light_eye = scale(direction, nearest_ray - 1.f);
+    const auto view = look_at(light_eye, add(light_eye, direction), up);
+    const auto depth = std::max(2.f, furthest_ray - nearest_ray + 2.f);
+    result.view_projection = multiply(orthographic(left, right, bottom, top, .1f, depth),
+                                      view);
+    return result;
+}
+ShadowView local_view(const LocalLight& light, std::uint32_t face,
+                      std::span<const ShadowCasterBounds> casters) {
+    ShadowView result;
+    result.kind = light.kind == LocalLight::Kind::Point ? ShadowView::Kind::Point
+                                                        : ShadowView::Kind::Spot;
+    result.light_id = light.stable_id;
+    result.face_index = face;
+    static constexpr std::array<Vec3, 6> axes{{{1, 0, 0}, {-1, 0, 0}, {0, 1, 0},
+                                                {0, -1, 0}, {0, 0, 1}, {0, 0, -1}}};
+    static constexpr std::array<Vec3, 6> ups{{{0, -1, 0}, {0, -1, 0}, {0, 0, 1},
+                                               {0, 0, -1}, {0, -1, 0}, {0, -1, 0}}};
+    const auto direction = light.kind == LocalLight::Kind::Point ? axes.at(face)
+                                                                 : unit(light.direction);
+    const auto up = light.kind == LocalLight::Kind::Point ? ups.at(face)
+                    : std::abs(direction[1]) > .98f ? Vec3{0, 0, 1} : Vec3{0, 1, 0};
+    const auto near_plane = std::max(.0001f, std::min(.05f, light.range * .1f));
+    const auto fov = light.kind == LocalLight::Kind::Point
+        ? std::numbers::pi_v<float> / 2 : light.outer_angle * 2;
+    result.view_projection = multiply(
+        perspective(fov, 1, near_plane, light.range),
+        look_at(light.position, add(light.position, direction), up));
+    result.caster_indices = visible_casters(result.view_projection, casters);
+    return result;
+}
+} // namespace
+
+ShadowPlan build_shadow_plan(const Snapshot& frame,
+                             std::span<const ShadowCasterBounds> casters,
+                             const ShadowBudget& budget) {
+    for (const auto& caster : casters)
+        for (int axis = 0; axis < 3; ++axis)
+            if (!std::isfinite(caster.world.min[axis]) ||
+                !std::isfinite(caster.world.max[axis]) ||
+                caster.world.min[axis] > caster.world.max[axis])
+                throw std::invalid_argument("Shadow caster world bounds must be finite and ordered");
+    ShadowPlan plan;
+    plan.sun_atlas_size = supported_atlas(budget.sun_atlas_size, budget.sun_atlas_available)
+        ? budget.sun_atlas_size : 0;
+    plan.local_atlas_size = supported_atlas(budget.local_atlas_size, budget.local_atlas_available)
+        ? budget.local_atlas_size : 0;
+    std::unordered_set<std::string> ids;
+    std::vector<std::pair<std::size_t, float>> ranked;
+    ranked.reserve(frame.local_lights.size());
+    for (std::size_t i = 0; i < frame.local_lights.size(); ++i) {
+        const auto& light = frame.local_lights[i];
+        validate_local(light); // Validate overflow records too, before truncation.
+        if (!ids.insert(light.stable_id).second)
+            throw std::invalid_argument("Duplicate local light stable_id: " + light.stable_id);
+        ranked.emplace_back(i, projected_influence(light, frame));
+    }
+    std::sort(ranked.begin(), ranked.end(), [&](const auto& a, const auto& b) {
+        const auto& left = frame.local_lights[a.first];
+        const auto& right = frame.local_lights[b.first];
+        if (left.shadow_priority != right.shadow_priority)
+            return left.shadow_priority > right.shadow_priority;
+        if (a.second != b.second)
+            return a.second > b.second;
+        return left.stable_id < right.stable_id;
+    });
+    const auto selected = std::min<std::size_t>(ranked.size(),
+                                                std::min(budget.max_local_lights, 128u));
+    plan.omitted_local_lights = static_cast<std::uint32_t>(ranked.size() - selected);
+    for (std::size_t i = 0; i < selected; ++i)
+        plan.submitted_local_indices.push_back(ranked[i].first);
+
+    std::optional<SunLight> sun = frame.sun;
+    if (!sun && !frame.authored_lights_present && frame.local_lights.empty())
+        sun = SunLight{"legacy-sun", frame.light_direction, {1, 1, 1, 1}, 1, true};
+    if (sun && sun->casts_shadow) {
+        plan.requested_sun_cascades = frame.camera_frustum
+            ? std::min(4u, budget.max_sun_views) : 1u;
+        if (frame.camera_frustum &&
+            (frame.camera_frustum->near_plane <= 0 ||
+             frame.camera_frustum->far_plane <= frame.camera_frustum->near_plane ||
+             frame.camera_frustum->projection[0] == 0 ||
+             frame.camera_frustum->projection[5] == 0))
+            throw std::invalid_argument("Shadow camera frustum is invalid");
+        const float near_plane = frame.camera_frustum ? frame.camera_frustum->near_plane : .1f;
+        const float far_plane = frame.camera_frustum
+            ? std::min(frame.camera_frustum->far_plane, budget.max_shadow_distance) : 80.f;
+        if (far_plane <= near_plane)
+            throw std::invalid_argument("Shadow distance does not reach the camera near plane");
+        float previous = near_plane;
+        for (std::uint32_t i = 0; i < plan.requested_sun_cascades; ++i) {
+            const auto ratio = float(i + 1) / float(plan.requested_sun_cascades);
+            const auto logarithmic = near_plane * std::pow(far_plane / near_plane, ratio);
+            const auto uniform = near_plane + (far_plane - near_plane) * ratio;
+            const auto split = i + 1 == plan.requested_sun_cascades
+                ? far_plane : .5f * (logarithmic + uniform);
+            ShadowView view;
+            if (plan.sun_atlas_size)
+                view = sun_view(frame, *sun, casters, previous, split, i, plan.sun_atlas_size);
+            else {
+                view.kind = ShadowView::Kind::Sun;
+                view.light_id = sun->stable_id;
+                view.face_index = i;
+                view.split_near = previous;
+                view.split_far = split;
+                view.reason = ShadowDropReason::Unavailable;
+            }
+            if (plan.sun_atlas_size &&
+                view.caster_indices.size() <=
+                    budget.max_caster_draws - std::min(plan.caster_draws, budget.max_caster_draws)) {
+                view.valid = true;
+                plan.caster_draws += static_cast<std::uint32_t>(view.caster_indices.size());
+                ++plan.effective_sun_cascades;
+            } else {
+                if (plan.sun_atlas_size)
+                    view.reason = ShadowDropReason::CasterBudget;
+                view.caster_indices.clear();
+                ++plan.dropped_sun_views;
+            }
+            plan.sun_views.push_back(std::move(view));
+            previous = split;
+        }
+    }
+    for (const auto source : plan.submitted_local_indices) {
+        const auto& light = frame.local_lights[source];
+        LocalShadowAssignment assignment;
+        assignment.source_index = source;
+        assignment.first_view = static_cast<std::uint32_t>(plan.local_views.size());
+        const auto faces = light.kind == LocalLight::Kind::Point ? 6u : 1u;
+        if (!light.casts_shadow || light.intensity == 0) {
+            plan.local_assignments.push_back(assignment);
+            continue;
+        }
+        plan.local_faces_requested += faces;
+        if (!plan.local_atlas_size)
+            assignment.reason = ShadowDropReason::Unavailable;
+        else if (const auto capacity = std::min(budget.max_local_faces, 16u);
+                 faces > capacity - std::min(plan.local_faces_used, capacity))
+            assignment.reason = ShadowDropReason::TileBudget;
+        else {
+            std::vector<ShadowView> group;
+            std::uint32_t group_draws{};
+            for (std::uint32_t face = 0; face < faces; ++face) {
+                auto view = local_view(light, face, casters);
+                tile(view, plan.local_atlas_size, 4,
+                     plan.local_faces_used + face);
+                group_draws += static_cast<std::uint32_t>(view.caster_indices.size());
+                group.push_back(std::move(view));
+            }
+            if (group_draws > budget.max_caster_draws -
+                                  std::min(plan.caster_draws, budget.max_caster_draws))
+                assignment.reason = ShadowDropReason::CasterBudget;
+            else {
+                assignment.valid = true;
+                assignment.face_count = faces;
+                plan.local_faces_used += faces;
+                plan.caster_draws += group_draws;
+                for (auto& view : group) {
+                    view.valid = true;
+                    plan.local_views.push_back(std::move(view));
+                }
+            }
+        }
+        if (!assignment.valid) {
+            plan.dropped_local_faces += faces;
+            if (light.kind == LocalLight::Kind::Point)
+                plan.dropped_point_faces += 6;
+        }
+        plan.local_assignments.push_back(assignment);
+    }
+    return plan;
+}
+} // namespace faset::render

src/render/renderer.cpp

@@ -6,14 +6,17 @@
 #include <bit>
 #include <chrono>
 #include <cmath>
+#include <cstddef>
 #include <cstring>
 #include <faset/core/io.hpp>
 #include <faset/render/render_graph.hpp>
+#include <faset/render/lighting.hpp>
 #include <faset/render/renderer.hpp>
 #include <faset/render/visibility.hpp>
 #include <fstream>
 #include <iostream>
 #include <limits>
+#include <numbers>
 #include <optional>
 #include <stdexcept>
 #include <unordered_map>
@@ -72,6 +75,40 @@ struct ScenePush {
     std::array<std::uint32_t, 4> draw_info;
 };
 static_assert(sizeof(ScenePush) == 112);
+struct LightingHeaderGpu {
+    std::array<std::uint32_t, 4> counts{};
+    std::array<float, 4> sun_direction_intensity{};
+    std::array<float, 4> sun_color{};
+    std::array<float, 4> camera_forward_shadow_distance{};
+    std::array<float, 4> cascade_splits{};
+};
+struct LocalLightGpu {
+    std::array<float, 4> position_range{};
+    std::array<float, 4> direction_cos_outer{};
+    std::array<float, 4> color_intensity{};
+    std::array<float, 4> cone_type_shadow_view{};
+    std::array<float, 4> reserved{};
+};
+struct ShadowViewGpu {
+    Mat4 view_projection{identity};
+    std::array<float, 4> tile_scale_offset{};
+    std::array<float, 4> guarded_clamp{};
+    std::array<float, 4> bias_flags{};
+};
+static_assert(sizeof(LightingHeaderGpu) == 80 &&
+              offsetof(LightingHeaderGpu, sun_direction_intensity) == 16 &&
+              offsetof(LightingHeaderGpu, sun_color) == 32 &&
+              offsetof(LightingHeaderGpu, camera_forward_shadow_distance) == 48 &&
+              offsetof(LightingHeaderGpu, cascade_splits) == 64);
+static_assert(sizeof(LocalLightGpu) == 80 &&
+              offsetof(LocalLightGpu, direction_cos_outer) == 16 &&
+              offsetof(LocalLightGpu, color_intensity) == 32 &&
+              offsetof(LocalLightGpu, cone_type_shadow_view) == 48 &&
+              offsetof(LocalLightGpu, reserved) == 64);
+static_assert(sizeof(ShadowViewGpu) == 112 &&
+              offsetof(ShadowViewGpu, tile_scale_offset) == 64 &&
+              offsetof(ShadowViewGpu, guarded_clamp) == 80 &&
+              offsetof(ShadowViewGpu, bias_flags) == 96);
 std::array<float, 4> point(const Mat4& m, std::array<float, 4> p) {
     std::array<float, 4> o{};
     for (int r = 0; r < 4; ++r)
@@ -196,6 +233,7 @@ struct Renderer::Impl {
     std::vector<VkImageLayout> swap_layouts;
     Image color, depth, shadow;
     Buffer vertices, readback;
+    Buffer lighting_header, lighting_locals, lighting_views;
     SceneResources scene;
     InstanceTracker instance_tracker;
     std::unordered_map<std::string, std::size_t> previous_lods;
@@ -212,6 +250,9 @@ struct Renderer::Impl {
     std::unordered_map<const Texture*, CachedOpacity> opacity_cache;
     VkDescriptorSetLayout descriptor_layout{};
     VkDescriptorPool descriptor_pool{};
+    VkDescriptorSetLayout lighting_layout{};
+    VkDescriptorPool lighting_pool{};
+    VkDescriptorSet lighting_set{};
     VkSampler shadow_sampler{}, color_sampler{};
     VkPipelineLayout pipeline_layout{};
     VkPipeline pipeline{}, ui_pipeline{}, shadow_pipeline{}, sprite_pipeline{};
@@ -316,6 +357,9 @@ struct Renderer::Impl {
         destroy(scene.hzb[1]);
         destroy(vertices);
         destroy(readback);
+        destroy(lighting_header);
+        destroy(lighting_locals);
+        destroy(lighting_views);
         destroy(color);
         destroy(depth);
         destroy(shadow);
@@ -333,8 +377,12 @@ struct Renderer::Impl {
                 vkDestroyPipelineLayout(device, pipeline_layout, nullptr);
             if (descriptor_pool)
                 vkDestroyDescriptorPool(device, descriptor_pool, nullptr);
+            if (lighting_pool)
+                vkDestroyDescriptorPool(device, lighting_pool, nullptr);
             if (descriptor_layout)
                 vkDestroyDescriptorSetLayout(device, descriptor_layout, nullptr);
+            if (lighting_layout)
+                vkDestroyDescriptorSetLayout(device, lighting_layout, nullptr);
             if (shadow_sampler)
                 vkDestroySampler(device, shadow_sampler, nullptr);
             if (color_sampler)
@@ -889,6 +937,31 @@ struct Renderer::Impl {
         pi.pPoolSizes = sizes;
         check(vkCreateDescriptorPool(device, &pi, nullptr, &descriptor_pool),
               "Create descriptor pool");
+        std::array<VkDescriptorSetLayoutBinding, 4> lighting_bindings{};
+        for (std::uint32_t i = 0; i < lighting_bindings.size(); ++i)
+            lighting_bindings[i] = {i,
+                                    i == 3 ? VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE
+                                           : VK_DESCRIPTOR_TYPE_STORAGE_BUFFER,
+                                    1, VK_SHADER_STAGE_FRAGMENT_BIT, nullptr};
+        li.bindingCount = static_cast<std::uint32_t>(lighting_bindings.size());
+        li.pBindings = lighting_bindings.data();
+        check(vkCreateDescriptorSetLayout(device, &li, nullptr, &lighting_layout),
+              "Create lighting descriptor layout");
+        VkDescriptorPoolSize lighting_sizes[] = {
+            {VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, 3}, {VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, 1}};
+        pi.flags = 0;
+        pi.maxSets = 1;
+        pi.poolSizeCount = 2;
+        pi.pPoolSizes = lighting_sizes;
+        check(vkCreateDescriptorPool(device, &pi, nullptr, &lighting_pool),
+              "Create lighting descriptor pool");
+        VkDescriptorSetAllocateInfo lighting_allocation{};
+        lighting_allocation.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_ALLOCATE_INFO;
+        lighting_allocation.descriptorPool = lighting_pool;
+        lighting_allocation.descriptorSetCount = 1;
+        lighting_allocation.pSetLayouts = &lighting_layout;
+        check(vkAllocateDescriptorSets(device, &lighting_allocation, &lighting_set),
+              "Allocate lighting descriptors");
         VkSamplerCreateInfo si{};
         si.sType = VK_STRUCTURE_TYPE_SAMPLER_CREATE_INFO;
         si.magFilter = si.minFilter = VK_FILTER_NEAREST;
@@ -1009,8 +1082,9 @@ struct Renderer::Impl {
                                  sizeof(Push)};
         VkPipelineLayoutCreateInfo li{};
         li.sType = VK_STRUCTURE_TYPE_PIPELINE_LAYOUT_CREATE_INFO;
-        li.setLayoutCount = 1;
-        li.pSetLayouts = &descriptor_layout;
+        const std::array<VkDescriptorSetLayout, 2> set_layouts{descriptor_layout, lighting_layout};
+        li.setLayoutCount = static_cast<std::uint32_t>(set_layouts.size());
+        li.pSetLayouts = set_layouts.data();
         li.pushConstantRangeCount = 1;
         li.pPushConstantRanges = &push;
         check(vkCreatePipelineLayout(device, &li, nullptr, &pipeline_layout),
@@ -1220,14 +1294,14 @@ struct Renderer::Impl {
         layout.pBindings = hzb.data();
         check(vkCreateDescriptorSetLayout(device, &layout, nullptr, &scene.hzb_layout),
               "Create HZB descriptor layout");
-        const std::array<VkDescriptorSetLayout, 2> scene_layouts{descriptor_layout,
-                                                                  scene.graphics_layout};
+        const std::array<VkDescriptorSetLayout, 3> scene_layouts{
+            descriptor_layout, lighting_layout, scene.graphics_layout};
         VkPushConstantRange graphics_push{VK_SHADER_STAGE_VERTEX_BIT |
                                               VK_SHADER_STAGE_FRAGMENT_BIT,
                                           0, sizeof(ScenePush)};
         VkPipelineLayoutCreateInfo pipeline_info{};
         pipeline_info.sType = VK_STRUCTURE_TYPE_PIPELINE_LAYOUT_CREATE_INFO;
-        pipeline_info.setLayoutCount = 2;
+        pipeline_info.setLayoutCount = static_cast<std::uint32_t>(scene_layouts.size());
         pipeline_info.pSetLayouts = scene_layouts.data();
         pipeline_info.pushConstantRangeCount = 1;
         pipeline_info.pPushConstantRanges = &graphics_push;
@@ -1533,6 +1607,29 @@ struct Renderer::Impl {
                              VkBufferUsageFlags usage = 0) {
         upload_scene_buffer(buffer, values.data(), values.size() * sizeof(T), usage);
     }
+    void update_lighting_descriptors() {
+        const std::array<VkDescriptorBufferInfo, 3> buffers{{
+            {lighting_header.handle, 0, lighting_header.size},
+            {lighting_locals.handle, 0, lighting_locals.size},
+            {lighting_views.handle, 0, lighting_views.size}}};
+        const VkDescriptorImageInfo atlas{VK_NULL_HANDLE, shadow.view,
+                                          VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_OPTIMAL};
+        std::array<VkWriteDescriptorSet, 4> writes{};
+        for (std::uint32_t i = 0; i < writes.size(); ++i) {
+            writes[i].sType = VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET;
+            writes[i].dstSet = lighting_set;
+            writes[i].dstBinding = i;
+            writes[i].descriptorCount = 1;
+            writes[i].descriptorType = i == 3 ? VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE
+                                               : VK_DESCRIPTOR_TYPE_STORAGE_BUFFER;
+            if (i == 3)
+                writes[i].pImageInfo = &atlas;
+            else
+                writes[i].pBufferInfo = &buffers[i];
+        }
+        vkUpdateDescriptorSets(device, static_cast<std::uint32_t>(writes.size()),
+                               writes.data(), 0, nullptr);
+    }
     void update_scene_descriptors(bool occlusion) {
         auto write_buffers = [&](VkDescriptorSet set, std::span<const Buffer* const> buffers,
                                  std::uint32_t first_binding) {
@@ -1625,6 +1722,7 @@ struct Renderer::Impl {
     void render(const Snapshot& snapshot) {
         auto start = std::chrono::steady_clock::now();
         statistics.draw_calls = statistics.culled_meshes = statistics.gpu_label_count = 0;
+        statistics.submitted_local_lights = statistics.omitted_local_lights = 0;
         statistics.gpu_bins = statistics.gpu_visible_instances =
             statistics.gpu_frustum_rejected = statistics.gpu_occlusion_deferred =
                 statistics.gpu_post_visible = 0;
@@ -1715,6 +1813,8 @@ struct Renderer::Impl {
         };
         std::vector<SelectedDraw> selected_draws;
         selected_draws.reserve(snapshot.draws.size());
+        std::vector<ShadowCasterBounds> shadow_casters;
+        shadow_casters.reserve(snapshot.draws.size());
         struct BuildingBin {
             const Mesh* mesh{};
             const Texture* texture{};
@@ -1724,10 +1824,17 @@ struct Renderer::Impl {
         std::vector<BuildingBin> building_bins;
         std::unordered_map<const Mesh*, std::pair<std::uint32_t, std::uint32_t>> mesh_ranges;
         std::unordered_map<std::string, std::size_t> current_lods;
-        for (const auto& item : snapshot.draws) {
+        for (std::size_t source_index = 0; source_index < snapshot.draws.size(); ++source_index) {
+            const auto& item = snapshot.draws[source_index];
             if (!item.mesh || item.mesh->vertices.empty())
                 continue;
             const auto source_bounds = world_bounds(item.mesh, item.model);
+            if (item.cast_shadow) {
+                if (source_index > UINT32_MAX)
+                    throw std::overflow_error("Shadow source draw index exceeds 32-bit capacity");
+                shadow_casters.push_back(
+                    {source_bounds, static_cast<std::uint32_t>(source_index)});
+            }
             std::vector<float> thresholds;
             std::vector<std::uint8_t> available;
             std::shared_ptr<const Mesh> selected_mesh = item.mesh;
@@ -2017,15 +2124,73 @@ struct Renderer::Impl {
                                     VK_BUFFER_USAGE_TRANSFER_DST_BIT);
             update_scene_descriptors(occlusion);
         }
-        Vec3 direction = snapshot.light_direction;
+        std::optional<SunLight> sun = snapshot.sun;
+        if (!sun && !snapshot.authored_lights_present && snapshot.local_lights.empty())
+            sun = SunLight{"legacy-sun", snapshot.light_direction, {1, 1, 1, 1}, 1, true};
+        Vec3 direction = sun ? sun->direction : snapshot.light_direction;
         float length = std::sqrt(direction[0] * direction[0] + direction[1] * direction[1] +
                                  direction[2] * direction[2]);
-        if (length < 1e-5f) {
+        if (!std::isfinite(length) || length < 1e-5f) {
+            if (sun && sun->stable_id != "legacy-sun")
+                throw std::invalid_argument("Authored sun direction must be finite and nonzero");
             direction = {-.5f, -1, -.3f};
             length = std::sqrt(1.34f);
         }
         for (auto& v : direction)
             v /= length;
+        LightingHeaderGpu lighting{};
+        lighting.counts[1] = sun ? 1u : 0u;
+        lighting.counts[2] = sun && sun->casts_shadow ? 1u : 0u;
+        lighting.sun_direction_intensity = {direction[0], direction[1], direction[2],
+                                            sun ? sun->intensity : 0};
+        lighting.sun_color = sun ? sun->color : Color{0, 0, 0, 1};
+        if (sun && (!std::isfinite(sun->intensity) || sun->intensity < 0 ||
+                    std::any_of(sun->color.begin(), sun->color.end(),
+                                [](float v) { return !std::isfinite(v) || v < 0; })))
+            throw std::invalid_argument("Authored sun radiance must be finite and nonnegative");
+        lighting.camera_forward_shadow_distance = {0, 0, -1, 80};
+        if (snapshot.camera_frustum) {
+            const auto& view = snapshot.camera_frustum->view;
+            lighting.camera_forward_shadow_distance = {-view[2], -view[6], -view[10], 80};
+        }
+        const auto shadow_plan = build_shadow_plan(snapshot, shadow_casters);
+        statistics.omitted_local_lights = shadow_plan.omitted_local_lights;
+        std::vector<LocalLightGpu> gpu_lights;
+        gpu_lights.reserve(shadow_plan.submitted_local_indices.size());
+        for (const auto source : shadow_plan.submitted_local_indices) {
+            const auto& local = snapshot.local_lights[source];
+            auto spot_direction = local.direction;
+            float spot_length = std::hypot(spot_direction[0], spot_direction[1],
+                                           spot_direction[2]);
+            if (!std::isfinite(spot_length) || spot_length < 1e-6f) {
+                if (local.kind == LocalLight::Kind::Spot)
+                    throw std::invalid_argument("Spotlight direction must be finite and nonzero");
+                spot_direction = {0, 0, -1};
+                spot_length = 1;
+            }
+            for (auto& axis : spot_direction)
+                axis /= spot_length;
+            LocalLightGpu gpu{};
+            gpu.position_range = {local.position[0], local.position[1], local.position[2],
+                                  local.range};
+            const bool spot = local.kind == LocalLight::Kind::Spot;
+            gpu.direction_cos_outer = {spot_direction[0], spot_direction[1], spot_direction[2],
+                                       spot ? std::cos(local.outer_angle) : 0.f};
+            gpu.color_intensity = {local.color[0], local.color[1], local.color[2],
+                                   local.intensity};
+            gpu.cone_type_shadow_view = {spot ? std::cos(local.inner_angle) : 1.f,
+                                         spot ? 1.f : 0.f, -1, 0};
+            gpu_lights.push_back(gpu);
+        }
+        lighting.counts[0] = static_cast<std::uint32_t>(gpu_lights.size());
+        statistics.submitted_local_lights = lighting.counts[0];
+        if (gpu_lights.empty())
+            gpu_lights.push_back({}); // Descriptors always point at a full initialized record.
+        const ShadowViewGpu empty_shadow_view{};
+        upload_scene_buffer(lighting_header, &lighting, sizeof(lighting), 0);
+        upload_scene_vector(lighting_locals, gpu_lights);
+        upload_scene_buffer(lighting_views, &empty_shadow_view, sizeof(empty_shadow_view), 0);
+        update_lighting_descriptors();
         Vec3 light_eye{-direction[0] * 30, -direction[1] * 30, -direction[2] * 30};
         Vec3 light_up = std::abs(direction[1]) > .98f ? Vec3{0, 0, 1} : Vec3{0, 1, 0};
         Push push{multiply(orthographic(-20, 20, -20, 20, .1f, 80),
@@ -2078,6 +2243,12 @@ struct Renderer::Impl {
             vkCmdSetViewport(command, 0, 1, &viewport);
             vkCmdSetScissor(command, 0, 1, &scissor);
         };
+        auto bind_material = [&](VkDescriptorSet material) {
+            const std::array<VkDescriptorSet, 2> sets{material, lighting_set};
+            vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline_layout,
+                                    0, static_cast<std::uint32_t>(sets.size()), sets.data(),
+                                    0, nullptr);
+        };
         auto draw_transparent = [&] {
             if (transparent_batches.empty())
                 return;
@@ -2088,8 +2259,7 @@ struct Renderer::Impl {
                                0, sizeof(push), &push);
             for (auto batch : transparent_batches) {
                 auto descriptor = textures.at(batch.texture).descriptor;
-                vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS,
-                                        pipeline_layout, 0, 1, &descriptor, 0, nullptr);
+                bind_material(descriptor);
                 vkCmdDraw(command, batch.count, 1, batch.first, 0);
                 ++statistics.draw_calls;
             }
@@ -2102,8 +2272,7 @@ struct Renderer::Impl {
                                sizeof(push), &push);
             for (auto batch : sprite_batches) {
                 auto descriptor = textures.at(batch.texture).descriptor;
-                vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline_layout,
-                                        0, 1, &descriptor, 0, nullptr);
+                bind_material(descriptor);
                 vkCmdDraw(command, batch.count, 1, batch.first, 0);
                 ++statistics.draw_calls;
             }
@@ -2125,8 +2294,7 @@ struct Renderer::Impl {
                     continue;
                 vkCmdSetScissor(command, 0, 1, &scissor);
                 auto descriptor = textures.at(batch.texture).descriptor;
-                vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline_layout,
-                                        0, 1, &descriptor, 0, nullptr);
+                bind_material(descriptor);
                 vkCmdDraw(command, batch.count, 1, batch.first, 0);
                 ++statistics.draw_calls;
             }
@@ -2313,8 +2481,7 @@ struct Renderer::Impl {
             vkCmdPushConstants(command, pipeline_layout,
                                VK_SHADER_STAGE_VERTEX_BIT | VK_SHADER_STAGE_FRAGMENT_BIT, 0,
                                sizeof(push), &push);
-            vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline_layout, 0, 1,
-                                    &white_descriptor, 0, nullptr);
+            bind_material(white_descriptor);
             if (gpu_active && !gpu_frame.bins.empty()) {
                 VkDeviceSize scene_offset{};
                 vkCmdBindVertexBuffers(command, 0, 1, &scene.vertices.handle, &scene_offset);
@@ -2322,7 +2489,7 @@ struct Renderer::Impl {
                                   scene.graphics_pipeline);
                 for (std::uint32_t bin = 0; bin < gpu_frame.bins.size(); ++bin) {
                     auto descriptor = textures.at(gpu_frame.textures[bin]).descriptor;
-                    const std::array<VkDescriptorSet, 2> sets{descriptor,
+                    const std::array<VkDescriptorSet, 3> sets{descriptor, lighting_set,
                                                                scene.graphics_main};
                     vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS,
                                             scene.graphics_pipeline_layout, 0, sets.size(),
@@ -2346,8 +2513,7 @@ struct Renderer::Impl {
             }
             for (auto batch : scene_batches) {
                 auto descriptor = textures.at(batch.texture).descriptor;
-                vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline_layout,
-                                        0, 1, &descriptor, 0, nullptr);
+                bind_material(descriptor);
                 vkCmdDraw(command, batch.count, 1, batch.first, 0);
                 ++statistics.draw_calls;
             }
@@ -2446,7 +2612,7 @@ struct Renderer::Impl {
                                       scene.graphics_pipeline);
                     for (std::uint32_t bin = 0; bin < gpu_frame.bins.size(); ++bin) {
                         auto descriptor = textures.at(gpu_frame.textures[bin]).descriptor;
-                        const std::array<VkDescriptorSet, 2> sets{descriptor,
+                        const std::array<VkDescriptorSet, 3> sets{descriptor, lighting_set,
                                                                    scene.graphics_post};
                         vkCmdBindDescriptorSets(command, VK_PIPELINE_BIND_POINT_GRAPHICS,
                                                 scene.graphics_pipeline_layout, 0,
@@ -2618,7 +2784,10 @@ struct Renderer::Impl {
         ++statistics.frame;
         statistics.gpu_allocated_bytes = vertices.allocation_size + readback.allocation_size +
                                          color.allocation_size + depth.allocation_size +
-                                         shadow.allocation_size;
+                                         shadow.allocation_size +
+                                         lighting_header.allocation_size +
+                                         lighting_locals.allocation_size +
+                                         lighting_views.allocation_size;
         statistics.texture_count = static_cast<std::uint32_t>(textures.size());
         for (const auto& [_, texture] : textures)
             statistics.gpu_allocated_bytes += texture.image.allocation_size;

src/render/shader_contract.cpp

@@ -34,13 +34,21 @@ void validate_layout(const Json& layout, std::string_view entry) {
     const bool fragment = entry == "fragmentMain";
     require(layout.at("stage") == (fragment ? "fragment" : "vertex"), "shader stage changed");
     const auto& descriptors = layout.at("descriptors");
-    require(descriptors.is_array() && descriptors.size() == 4, "descriptor count changed");
+    require(descriptors.is_array() && descriptors.size() == 8, "descriptor count changed");
     for (std::size_t i = 0; i < descriptors.size(); ++i) {
         const auto& binding = descriptors[i];
-        require(binding.at("set") == 0 && binding.at("binding") == i && binding.at("count") == 1,
+        const auto set = i < 4 ? 0 : 1;
+        const auto slot = i % 4;
+        require(binding.at("set") == set && binding.at("binding") == slot &&
+                    binding.at("count") == 1,
                 "descriptor set, binding or array count changed");
-        require(binding.at("type") == (i % 2 ? "sampler" : "sampled_image_2d"),
+        const auto* expected_type = set == 0 ? (slot % 2 ? "sampler" : "sampled_image_2d")
+                                    : slot == 3 ? "sampled_image_2d" : "storage_buffer";
+        require(binding.at("type") == expected_type,
                 "descriptor type changed");
+        if (set == 1 && slot < 3)
+            require(binding.at("element_stride") == (slot == 2 ? 112 : 80),
+                    "lighting storage record stride changed");
         require(fragment || !binding.at("used").get<bool>(),
                 "vertex texture bindings are unsupported");
     }
@@ -98,7 +106,7 @@ void validate_gpu_layout(const Json& layout, std::string_view entry) {
     const std::array<int, 3> graphics_strides{224, 4, 208};
     for (std::size_t i = 0; i < expected_count; ++i) {
         const auto& binding = descriptors[i];
-        require(binding.at("set") == (graphics ? 1 : 0) && binding.at("binding") == i &&
+        require(binding.at("set") == (graphics ? 2 : 0) && binding.at("binding") == i &&
                     binding.at("count") == 1,
                 "GPU descriptor set, binding or count changed");
         const int stride = graphics ? graphics_strides[i] : hzb ? 0 : compute_strides[i];

tests/authoring_tests.cpp

@@ -2,6 +2,7 @@
 #include <faset/authoring/templates.hpp>
 #include <faset/authoring/transforms.hpp>
 #include <faset/core/io.hpp>
+#include <cstdint>
 #include <iostream>
 
 #define CHECK(x)                                                                                   \
@@ -25,6 +26,32 @@ int main() {
     const auto root = std::filesystem::temp_directory_path() / ("faset-authoring-" + new_id());
     try {
         auto schemas = builtin_schemas();
+        const auto light = schemas.schema("faset.light");
+        CHECK(light["version"] == 1);
+        const auto defaults = schemas.default_fields("faset.light");
+        CHECK(defaults["kind"] == "directional");
+        CHECK(defaults["enabled"] == true);
+        CHECK(defaults["range"] == 10.0);
+        CHECK(defaults["inner_angle"] < defaults["outer_angle"]);
+        CHECK(defaults["casts_shadow"] == true);
+        CHECK(defaults["shadow_priority"] == 0);
+        auto light_component = Json{{"type", "faset.light"}, {"version", 1}, {"fields", defaults}};
+        schemas.validate_component(light_component);
+        light_component["fields"]["kind"] = "area";
+        fails([&] { schemas.validate_component(light_component); }, "validation.enum");
+        light_component["fields"]["kind"] = "point";
+        light_component["fields"]["range"] = 0;
+        fails([&] { schemas.validate_component(light_component); }, "validation.minimum");
+        light_component["fields"]["range"] = 10;
+        light_component["fields"]["intensity"] = -1;
+        fails([&] { schemas.validate_component(light_component); }, "validation.minimum");
+        light_component["fields"] = {{"kind", "spot"}, {"inner_angle", 0.9}};
+        fails([&] { schemas.validate_component(light_component); }, "validation.light_cone");
+        light_component["fields"] = {{"kind", "spot"},
+                                      {"inner_angle", 0.2},
+                                      {"outer_angle", 0.5},
+                                      {"shadow_priority", std::int64_t{2147483648}}};
+        fails([&] { schemas.validate_component(light_component); }, "validation.maximum");
         AuthoringService service(root, schemas);
         auto created = service.create("Courtyard", 3);
         const std::string id = created["id"];

tests/render_gpu_shader_contract_tests.cpp

@@ -59,6 +59,15 @@ int main() {
         faset::atomic_write_json(reflection_file, metadata);
         must_reject([&] { (void)faset::render::detail::load_gpu_shader_bundle(temporary); },
                     "A consistently rehashed but incompatible GPU record stride must be rejected");
+        faset::atomic_write_json(reflection_file,
+                                 faset::read_json(original / "gpuPostCullMain.reflection.json"));
+        reflection_file = temporary / "gpuVertexMain.reflection.json";
+        metadata = faset::read_json(original / "gpuVertexMain.reflection.json");
+        metadata["layout"]["descriptors"][0]["set"] = 1;
+        metadata["layout_fingerprint"] = faset::sha256(metadata["layout"].dump());
+        faset::atomic_write_json(reflection_file, metadata);
+        must_reject([&] { (void)faset::render::detail::load_gpu_shader_bundle(temporary); },
+                    "GPU graphics scene buffers must stay in descriptor set two");
         fs::remove(temporary / "gpuHzbMain.spv");
         must_reject([&] { (void)faset::render::detail::load_gpu_shader_bundle(temporary); },
                     "Missing P2 entry must be rejected");

tests/render_lighting_policy_tests.cpp

@@ -0,0 +1,191 @@
+#include <faset/render/lighting.hpp>
+#include <algorithm>
+#include <array>
+#include <cmath>
+#include <iostream>
+#include <stdexcept>
+
+using namespace faset::render;
+namespace {
+void require(bool condition, const char* message) {
+    if (!condition)
+        throw std::runtime_error(message);
+}
+Snapshot fixture() {
+    Snapshot frame;
+    const Vec3 eye{0, 2, 8};
+    const auto view = look_at(eye, {0, 0, 0});
+    const auto projection = perspective(.9f, 16.f / 9.f, .1f, 120.f);
+    frame.eye = eye;
+    frame.view_projection = multiply(projection, view);
+    frame.projection = projection;
+    frame.camera_frustum = CameraFrustum{view, projection, .1f, 120.f, true};
+    frame.authored_lights_present = true;
+    frame.sun = SunLight{"sun", {-.7f, -.5f, -.3f}, {1, 1, 1, 1}, 1, true};
+    return frame;
+}
+LocalLight point_light(std::string id, int priority = 0) {
+    LocalLight light;
+    light.kind = LocalLight::Kind::Point;
+    light.stable_id = std::move(id);
+    light.position = {0, 2, 0};
+    light.range = 12;
+    light.shadow_priority = priority;
+    return light;
+}
+LocalLight spot_light(std::string id, int priority = 0) {
+    auto light = point_light(std::move(id), priority);
+    light.kind = LocalLight::Kind::Spot;
+    light.direction = {0, -1, 0};
+    return light;
+}
+bool contains_caster(const ShadowView& view, std::uint32_t draw_index) {
+    return std::find(view.caster_indices.begin(), view.caster_indices.end(), draw_index) !=
+           view.caster_indices.end();
+}
+void run() {
+    auto frame = fixture();
+    const auto plan = build_shadow_plan(frame, {}, {});
+    require(plan.sun_views.size() == 4 && plan.effective_sun_cascades == 4,
+            "Explicit camera receives four usable sun cascades");
+    require(plan.sun_views[0].split_near == .1f &&
+                std::abs(plan.sun_views.back().split_far - 80.f) < 1e-4f,
+            "Practical splits start at camera near and stop at shadow distance");
+    for (std::size_t i = 1; i < plan.sun_views.size(); ++i)
+        require(plan.sun_views[i].split_near == plan.sun_views[i - 1].split_far &&
+                    plan.sun_views[i].split_far > plan.sun_views[i].split_near,
+                "Cascade split endpoints are strictly increasing and contiguous");
+    require(plan.sun_views[0].tile_index == 0 && plan.sun_views[3].tile_index == 3 &&
+                plan.sun_views[0].usable_size == 1020,
+            "Four guarded 1024-square tiles fit a 2048-square sun atlas");
+    auto shifted = frame;
+    shifted.eye[0] += .00001f;
+    const auto shifted_view = look_at(shifted.eye, {.00001f, 0, 0});
+    shifted.camera_frustum->view = shifted_view;
+    shifted.view_projection = multiply(shifted.projection, shifted_view);
+    const auto stable = build_shadow_plan(shifted, {}, {});
+    require(stable.sun_views[0].snapped_center_x == plan.sun_views[0].snapped_center_x &&
+                stable.sun_views[0].snapped_center_y == plan.sun_views[0].snapped_center_y,
+            "Subtexel camera translation retains the snapped sun projection origin");
+    const auto sun_direction = frame.sun->direction;
+    const auto inv_length = 1.f / std::hypot(sun_direction[0], sun_direction[1], sun_direction[2]);
+    const Vec3 upstream{-sun_direction[0] * inv_length * 18,
+                        -sun_direction[1] * inv_length * 18,
+                        -sun_direction[2] * inv_length * 18};
+    const ShadowCasterBounds offscreen{{{upstream[0] - .5f, upstream[1] - .5f,
+                                          upstream[2] - .5f},
+                                         {upstream[0] + .5f, upstream[1] + .5f,
+                                          upstream[2] + .5f}}, 7};
+    const ShadowCasterBounds outside{{{999, 0, 0}, {1001, 2, 2}}, 8};
+    const std::array casters{offscreen, outside};
+    const auto with_casters = build_shadow_plan(frame, casters, {});
+    require(std::any_of(with_casters.sun_views.begin(), with_casters.sun_views.end(),
+                        [](const auto& view) { return contains_caster(view, 7); }),
+            "Offscreen upstream caster remains in a receiver's sun shadow view");
+    require(std::none_of(with_casters.sun_views.begin(), with_casters.sun_views.end(),
+                         [](const auto& view) { return contains_caster(view, 8); }),
+            "Caster outside every sun XY footprint is excluded");
+    std::vector<ShadowCasterBounds> many(4097, {{{-.1f, -.1f, -.1f}, {.1f, .1f, .1f}}, 0});
+    for (std::uint32_t i = 0; i < many.size(); ++i)
+        many[i].draw_index = i;
+    const auto overdraw = build_shadow_plan(frame, many, {});
+    require(overdraw.caster_draws <= 4096 &&
+                std::any_of(overdraw.sun_views.begin(), overdraw.sun_views.end(),
+                            [](const auto& view) {
+                                return !view.valid && view.reason == ShadowDropReason::CasterBudget &&
+                                       view.caster_indices.empty();
+                            }),
+            "A view with 4097 casters is skipped whole rather than partially rendered");
+    frame.sun.reset();
+    for (int i = 0; i < 15; ++i)
+        frame.local_lights.push_back(spot_light("spot-" + std::to_string(i), 10));
+    frame.local_lights.push_back(point_light("last-point"));
+    const auto capacity = build_shadow_plan(frame, {}, {});
+    require(capacity.local_faces_used == 15 && capacity.dropped_point_faces == 6 &&
+                capacity.local_faces_used <= 16 && capacity.caster_draws <= 4096,
+            "Insufficient room for six point faces drops the complete point shadow");
+    require(capacity.submitted_local_indices.size() == 16 &&
+                std::none_of(capacity.local_views.begin(), capacity.local_views.end(),
+                             [](const auto& view) { return view.light_id == "last-point"; }),
+            "Atlas overflow leaves the point light in the lighting list, unshadowed");
+    frame.local_lights = {point_light("omnidirectional")};
+    const ShadowCasterBounds positive_x{{{3, -.2f, -.2f}, {3.4f, .2f, .2f}}, 19};
+    const auto point_faces = build_shadow_plan(frame, std::array{positive_x}, {});
+    require(point_faces.local_views.size() == 6 &&
+                contains_caster(point_faces.local_views[0], 19) &&
+                !contains_caster(point_faces.local_views[1], 19),
+            "Point-light caster behind the opposite face is culled from that face");
+    frame.local_lights.clear();
+    for (int i = 0; i < 15; ++i)
+        frame.local_lights.push_back(spot_light("spot-" + std::to_string(i), 10));
+    frame.local_lights.push_back(point_light("last-point"));
+    auto reversed = frame;
+    std::reverse(reversed.local_lights.begin(), reversed.local_lights.end());
+    const auto reordered = build_shadow_plan(reversed, {}, {});
+    require(reordered.local_views.size() == capacity.local_views.size(),
+            "Reversing input lights preserves scheduled view count");
+    for (std::size_t i = 0; i < capacity.local_views.size(); ++i)
+        require(reordered.local_views[i].light_id == capacity.local_views[i].light_id &&
+                    reordered.local_views[i].tile_index == capacity.local_views[i].tile_index,
+                "Stable IDs preserve atlas assignments across input reordering");
+    frame.local_lights.clear();
+    for (int i = 0; i < 128; ++i) {
+        auto light = spot_light("ordinary-" + std::to_string(i));
+        light.casts_shadow = false;
+        frame.local_lights.push_back(light);
+    }
+    auto important = spot_light("late-high-priority", 5);
+    important.casts_shadow = false;
+    frame.local_lights.push_back(important);
+    const auto ranked = build_shadow_plan(frame, {}, {});
+    require(ranked.submitted_local_indices.size() == 128 &&
+                ranked.omitted_local_lights == 1 &&
+                ranked.submitted_local_indices.front() == 128,
+            "Submission selects all 128 by priority and reports one omitted light");
+    frame.local_lights.back().range = -1;
+    bool invalid_overflow_rejected = false;
+    try {
+        (void)build_shadow_plan(frame, {}, {});
+    } catch (const std::invalid_argument&) {
+        invalid_overflow_rejected = true;
+    }
+    require(invalid_overflow_rejected,
+            "All authored lights are validated even when beyond the submission cap");
+    frame.local_lights.clear();
+    frame.sun.reset();
+    const auto no_sun = build_shadow_plan(frame, {}, {});
+    require(no_sun.requested_sun_cascades == 0 && no_sun.sun_views.empty(),
+            "Authored lights suppress legacy sun even when none is enabled");
+    for (int i = 0; i < 20; ++i)
+        frame.local_lights.push_back(spot_light("over-cap-" + std::to_string(i)));
+    ShadowBudget relaxed;
+    relaxed.max_local_faces = 64;
+    relaxed.max_local_lights = 256;
+    const auto clamped = build_shadow_plan(frame, {}, relaxed);
+    require(clamped.local_faces_used == 16 && clamped.dropped_local_faces == 4,
+            "Fixed 4x4 local atlas never allocates outside its sixteen tiles");
+    frame = fixture();
+    frame.camera_frustum.reset();
+    const auto legacy = build_shadow_plan(frame, {}, {});
+    require(legacy.sun_views.size() == 1 && legacy.effective_sun_cascades == 1,
+            "A low-level snapshot without camera frustum uses one reported sun view");
+    frame = fixture();
+    ShadowBudget unsupported;
+    unsupported.sun_atlas_available = false;
+    const auto no_atlas = build_shadow_plan(frame, {}, unsupported);
+    require(no_atlas.effective_sun_cascades == 0 &&
+                no_atlas.dropped_sun_views == 4 &&
+                no_atlas.sun_views[0].reason == ShadowDropReason::Unavailable,
+            "Unsupported depth atlas yields an explicit unshadowed sun fallback");
+}
+} // namespace
+int main() {
+    try {
+        run();
+        std::cout << "Shadow planning, stable allocation, caster visibility, and budgets passed\n";
+        return 0;
+    } catch (const std::exception& error) {
+        std::cerr << error.what() << '\n';
+        return 1;
+    }
+}

tests/render_reload_tests.cpp

@@ -59,6 +59,27 @@ int main() {
         const auto original_reflection = read_text(bundle / "fragmentMain.reflection.json");
         const auto original_fingerprint = Json::parse(original_reflection).at("layout_fingerprint");
         render::validate_shader_bundle(bundle);
+        auto bad_lighting_stride = Json::parse(original_reflection);
+        auto& lighting_descriptors = bad_lighting_stride["layout"]["descriptors"];
+        bool found_local_buffer = false;
+        for (auto& descriptor : lighting_descriptors)
+            if (descriptor["set"] == 1 && descriptor["binding"] == 1) {
+                descriptor["element_stride"] = 96;
+                found_local_buffer = true;
+            }
+        require(found_local_buffer, "Lighting stride fixture exists");
+        bad_lighting_stride["layout_fingerprint"] =
+            sha256(bad_lighting_stride["layout"].dump());
+        atomic_write_json(bundle / "fragmentMain.reflection.json", bad_lighting_stride);
+        bool rejected_lighting_stride = false;
+        try {
+            render::validate_shader_bundle(bundle);
+        } catch (const std::exception&) {
+            rejected_lighting_stride = true;
+        }
+        require(rejected_lighting_stride,
+                "Rehashed incompatible local-light element stride must be rejected");
+        atomic_write(bundle / "fragmentMain.reflection.json", original_reflection);
         render::RendererConfig configuration;
         configuration.width = configuration.height = 64;
         configuration.headless = true;
@@ -161,6 +182,18 @@ int main() {
         atomic_write(bundle / "fragmentMain.spv", "damaged bytecode");
         retained();
         restore();
+        auto incompatible = original_source;
+        auto at = incompatible.find("    float4 reserved;");
+        require(at != std::string::npos, "Local-light stride fixture exists");
+        incompatible.replace(at, std::string("    float4 reserved;").size(),
+                             "    float4 reserved;\n    float4 incompatibleExtraLane;");
+        atomic_write(source, incompatible);
+        require(compile(source, bundle) == 0, "Compile incompatible light-buffer stride");
+        require(read_json(bundle / "fragmentMain.reflection.json").at("layout_fingerprint") !=
+                    original_fingerprint,
+                "Lighting stride edit changes normalized layout fingerprint");
+        retained();
+        restore();
         auto malformed = original_spirv;
         for (int i = 0; i < 4; ++i)
             malformed[20 + i] = 0; // zero-word SPIR-V instruction
@@ -170,8 +203,8 @@ int main() {
         atomic_write_json(bundle / "fragmentMain.reflection.json", metadata);
         retained();
         restore();
-        auto incompatible = original_source;
-        auto at = incompatible.find("[[vk::binding(2,0)]]");
+        incompatible = original_source;
+        at = incompatible.find("[[vk::binding(2,0)]]");
         require(at != std::string::npos, "Shader descriptor fixture exists");
         incompatible.replace(at, std::string("[[vk::binding(2,0)]]").size(),
                              "[[vk::binding(7,0)]]");

tests/render_tests.cpp

@@ -134,6 +134,102 @@ int main(int argc, char** argv) {
         renderer.render(scene);
         pixels = renderer.pixels();
         require(pixels[index + 2] > 220, "Texture revision upload");
+        Snapshot two_lights;
+        two_lights.eye = {0, 0, 6};
+        two_lights.projection = perspective(.85f, 320.f / 240.f, .1f, 30.f);
+        two_lights.view_projection =
+            multiply(two_lights.projection, look_at(two_lights.eye, {0, 0, 0}));
+        two_lights.authored_lights_present = true;
+        two_lights.draws.push_back(
+            {cube_mesh(), transform({-1.4f, 0, 0}), {.5f, .5f, .5f, 1}, .6f, 0, false});
+        two_lights.draws.back().instance_key = "left-light-receiver";
+        two_lights.draws.push_back(
+            {cube_mesh(), transform({1.4f, 0, 0}), {.5f, .5f, .5f, 1}, .6f, 0, false});
+        two_lights.draws.back().instance_key = "right-light-receiver";
+        two_lights.ui_quads.push_back({8, 8, 40, 20, {.8f, .1f, .15f, 1}});
+        for (auto mode : {VisibilityMode::Direct, VisibilityMode::GpuFrustum}) {
+            renderer.set_visibility_mode(mode);
+            renderer.render(two_lights);
+            const auto dark = renderer.pixels();
+            require(renderer.stats().validation_errors == 0,
+                    "Zero-local-light descriptors are initialized");
+            auto legacy_lights = two_lights;
+            legacy_lights.authored_lights_present = false;
+            renderer.render(legacy_lights);
+            const auto legacy = renderer.pixels();
+            const auto left = (120 * 320 + 99) * 4;
+            require(legacy[left] > dark[left] + 15,
+                    "Authored-light presence suppresses the legacy sun even without a local light");
+            two_lights.local_lights = {
+                {LocalLight::Kind::Point, "red", {-1.4f, 0, 1.4f}, {0, 0, -1},
+                 {1, 0, 0, 1}, 8, 2.2f, .35f, .7f, false, 0},
+                {LocalLight::Kind::Point, "blue", {1.4f, 0, 1.4f}, {0, 0, -1},
+                {0, 0, 1, 1}, 8, 2.5f, .35f, .7f, false, 0}};
+            renderer.render(two_lights);
+            const auto lit = renderer.pixels();
+            const auto right = (120 * 320 + 221) * 4;
+            const auto ui = (10 * 320 + 10) * 4;
+            require(lit[left] > dark[left] + 20 && lit[right + 2] > dark[right + 2] + 20,
+                    "Separated red and blue point lights illuminate their receivers");
+            require(std::abs(int(lit[left + 2]) - int(dark[left + 2])) < 6 &&
+                        std::abs(int(lit[right]) - int(dark[right])) < 6,
+                    "Local light range keeps the opposite colored light off each receiver");
+            for (int channel = 0; channel < 4; ++channel)
+                require(lit[ui + channel] == dark[ui + channel],
+                        "Lighting changes leave UI tint unchanged");
+            require(renderer.stats().validation_errors == 0,
+                    "Direct and GPU local lighting report no Vulkan errors");
+            if (mode == VisibilityMode::GpuFrustum)
+                require(renderer.stats().effective_visibility_mode == VisibilityMode::GpuFrustum,
+                        "Local light image test actually exercises the GPU visibility path");
+            two_lights.local_lights[1].kind = LocalLight::Kind::Spot;
+            renderer.render(two_lights);
+            const auto aimed = renderer.pixels();
+            two_lights.local_lights[1].direction = {1, 0, 0};
+            renderer.render(two_lights);
+            const auto turned = renderer.pixels();
+            require(aimed[right + 2] > turned[right + 2] + 20,
+                    "Spotlight cone direction changes receiver illumination");
+            two_lights.local_lights.clear();
+        }
+        renderer.set_visibility_mode(VisibilityMode::Direct);
+        renderer.render(two_lights);
+        const auto unlit_overflow = renderer.pixels();
+        for (int i = 0; i < 128; ++i) {
+            LocalLight local;
+            local.stable_id = "low-priority-" + std::to_string(i);
+            local.position = {20, 20, 20};
+            local.range = 1;
+            local.intensity = 0;
+            local.casts_shadow = false;
+            two_lights.local_lights.push_back(local);
+        }
+        LocalLight high;
+        high.stable_id = "last-high-priority";
+        high.position = {-1.4f, 0, 1.4f};
+        high.color = {1, 0, 0, 1};
+        high.range = 2.2f;
+        high.intensity = 8;
+        high.shadow_priority = 10;
+        high.casts_shadow = false;
+        two_lights.local_lights.push_back(high);
+        two_lights.local_lights.back().range = -1;
+        bool overflow_validation_failed = false;
+        try {
+            renderer.render(two_lights);
+        } catch (const std::invalid_argument&) {
+            overflow_validation_failed = true;
+        }
+        require(overflow_validation_failed,
+                "Renderer validates light records beyond the 128-light cap");
+        two_lights.local_lights.back().range = 2.2f;
+        renderer.render(two_lights);
+        const auto ranked_pixels = renderer.pixels();
+        const auto ranked_left = (120 * 320 + 99) * 4;
+        require(renderer.stats().submitted_local_lights == 128 &&
+                    renderer.stats().omitted_local_lights == 1 &&
+                    ranked_pixels[ranked_left] > unlit_overflow[ranked_left] + 20,
+                "High-priority last light is submitted and omitted count is observable");
         if (argc > 2)
             renderer.capture(argv[2]);
         renderer.resize(400, 300);

tests/runtime_player_tests.cpp

@@ -1,10 +1,12 @@
 #include <bit>
+#include <algorithm>
 #include <cmath>
 #include <faset/assets/asset_pipeline.hpp>
 #include <faset/core/io.hpp>
 #include <faset/player/SceneView.hpp>
 #include <faset/runtime/Runtime.hpp>
 #include <iostream>
+#include <limits>
 #include <numbers>
 #include <stdexcept>
 
@@ -23,12 +25,137 @@ template <class F> void rejects(F&& function, const char* message) {
     }
     check(caught, message);
 }
+template <class F>
+void rejectsContaining(F&& function, std::string_view entityId, std::string_view field) {
+    try {
+        function();
+    } catch (const std::exception& error) {
+        const std::string_view what(error.what());
+        check(what.find(entityId) != std::string_view::npos &&
+                  what.find(field) != std::string_view::npos,
+              "Invalid light reports entity and field");
+        return;
+    }
+    throw std::runtime_error("Invalid light was accepted");
+}
 Json component(std::string type, Json fields) {
     return {{"id", type}, {"type", type}, {"version", 1}, {"fields", fields}};
 }
 Json entity(std::string id, Json parent, Json components) {
     return {{"id", id}, {"name", id}, {"parent", parent}, {"components", components}};
 }
+void lightingExtraction(faset::player::SceneView& view) {
+    auto scene = Json{{"format", "faset.scene"},
+                      {"version", 1},
+                      {"id", "lighting"},
+                      {"name", "Lighting"},
+                      {"dimension", 3},
+                      {"instances", Json::array()},
+                      {"entities", Json::array()}};
+    const auto empty = view.build(scene, 16.f / 9.f);
+    check(!empty.authored_lights_present && !empty.sun && empty.local_lights.empty(),
+          "Scene with no lights leaves legacy sun fallback available");
+    check(empty.camera_frustum && empty.camera_frustum->perspective &&
+              empty.camera_frustum->near_plane > 0 &&
+              empty.camera_frustum->far_plane > empty.camera_frustum->near_plane &&
+              faset::render::multiply(empty.camera_frustum->projection,
+                                      empty.camera_frustum->view) == empty.view_projection,
+          "3D extraction retains an unjittered camera frustum");
+    scene["entities"] = Json::array({
+        entity("sun", nullptr,
+               Json::array({component("faset.transform", {{"rotation", {0, .4, 0}}}),
+                            component("faset.light", {{"kind", "directional"},
+                                                      {"color", {1, .8, .6, 1}},
+                                                      {"intensity", 2.5},
+                                                      {"casts_shadow", false}})})),
+        entity("point", nullptr,
+               Json::array({component("faset.transform", {{"position", {2, 3, 4}}}),
+                            component("faset.light", {{"kind", "point"},
+                                                      {"color", {1, 0, 0, 1}},
+                                                      {"intensity", 4},
+                                                      {"range", 6},
+                                                      {"shadow_priority", 3}})})),
+        entity("spot", nullptr,
+               Json::array({component("faset.transform", {{"position", {-2, 1, 0}}}),
+                            component("faset.light", {{"kind", "spot"},
+                                                      {"color", {0, 0, 1, 1}},
+                                                      {"intensity", 3},
+                                                      {"range", 8},
+                                                      {"inner_angle", .2},
+                                                      {"outer_angle", .6}})}))});
+    const auto a = view.build(scene, 16.f / 9.f);
+    check(a.authored_lights_present && a.sun && a.local_lights.size() == 2,
+          "Directional, point, and spot lights survive extraction");
+    check(a.sun->color[1] == .8f && a.sun->intensity == 2.5f && !a.sun->casts_shadow,
+          "Authored sun properties survive extraction");
+    check(a.local_lights[0].kind == faset::render::LocalLight::Kind::Point &&
+              a.local_lights[0].position == faset::render::Vec3{2, 3, 4} &&
+              a.local_lights[0].range == 6 && a.local_lights[0].shadow_priority == 3,
+          "Point fields and transform survive extraction");
+    check(a.local_lights[1].kind == faset::render::LocalLight::Kind::Spot &&
+              a.local_lights[1].inner_angle == .2f && a.local_lights[1].outer_angle == .6f,
+          "Spot cone survives extraction");
+    std::reverse(scene["entities"].begin(), scene["entities"].end());
+    const auto b = view.build(scene, 16.f / 9.f);
+    check(a.sun->stable_id == b.sun->stable_id &&
+              a.local_lights[0].stable_id == b.local_lights[0].stable_id &&
+              a.local_lights[1].stable_id == b.local_lights[1].stable_id,
+          "Light identity and ordering ignore entity array order");
+    scene["entities"].erase(scene["entities"].begin() + 2);
+    const auto localOnly = view.build(scene, 1);
+    check(localOnly.authored_lights_present && !localOnly.sun &&
+              localOnly.local_lights.size() == 2,
+          "Local-only lighting does not synthesize a sun");
+    scene["entities"] = Json::array({entity(
+        "disabled-sun", nullptr,
+        Json::array({component("faset.light", {{"kind", "directional"}, {"enabled", false}})}))});
+    const auto disabled = view.build(scene, 1);
+    check(disabled.authored_lights_present && !disabled.sun && disabled.local_lights.empty(),
+          "Explicit disabled sun suppresses legacy fallback");
+    scene["entities"][0]["components"][0]["version"] = 2;
+    const auto future = view.build(scene, 1);
+    check(future.authored_lights_present && !future.sun,
+          "Opaque future-version light still suppresses legacy fallback");
+    scene["entities"] = Json::array({
+        entity("sun-z", nullptr, Json::array({component("faset.light", Json::object())})),
+        entity("sun-a", nullptr, Json::array({component("faset.light", Json::object())}))});
+    const auto twoSuns = view.build(scene, 1);
+    check(twoSuns.sun && twoSuns.sun->stable_id.find("sun-a") != std::string::npos,
+          "Multiple suns select lowest stable identity");
+    check(!view.diagnostics().empty() &&
+              view.diagnostics().front().find("directional") != std::string::npos,
+          "Additional directionals produce an actionable diagnostic");
+    scene["entities"] = Json::array({entity(
+        "bad-light", nullptr,
+        Json::array({component("faset.light", {{"kind", "point"}, {"range", 0}})}))});
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "range");
+    scene["entities"][0]["components"][0]["fields"] =
+        {{"kind", "spot"}, {"range", 10}, {"inner_angle", .8}, {"outer_angle", .2}};
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "inner_angle");
+    scene["entities"][0]["components"][0]["fields"] = {{"kind", "area"}};
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "kind");
+    scene["entities"][0]["components"][0]["fields"] =
+        {{"kind", "point"}, {"shadow_priority", std::int64_t{2147483648}}};
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "shadow_priority");
+    scene["entities"][0]["components"][0]["fields"] = {{"kind", "point"}};
+    scene["entities"][0]["components"].insert(
+        scene["entities"][0]["components"].begin(),
+        component("faset.transform", {{"scale", {1, 1, 0}}}));
+    const auto flatPoint = view.build(scene, 1);
+    check(flatPoint.local_lights.size() == 1 &&
+              flatPoint.local_lights[0].kind == faset::render::LocalLight::Kind::Point,
+          "Point light accepts a zero Z scale because it needs only a position");
+    scene["entities"][0]["components"].erase(scene["entities"][0]["components"].begin());
+    scene["entities"][0]["components"][0]["fields"] =
+        {{"kind", "point"},
+         {"color", Json::array({1, std::numeric_limits<double>::quiet_NaN(), 1, 1})}};
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "color");
+    scene["entities"][0]["components"].insert(
+        scene["entities"][0]["components"].begin(),
+        component("faset.transform", {{"position", {0, 0, 0}},
+                                       {"scale", Json::array({1, std::numeric_limits<double>::quiet_NaN(), 1})}}));
+    rejectsContaining([&] { view.build(scene, 1); }, "bad-light", "transform");
+}
 void physicsDebug(faset::player::SceneView& view) {
     for (int dimension : {2, 3}) {
         const std::string bodyName = dimension == 2 ? "rigid_body_2d" : "rigid_body_3d";
@@ -159,6 +286,7 @@ void run() {
     faset::atomic_write(folder / "version.fscene", version);
     rejects([&] { faset::player::readScene(folder / "version.fscene"); }, "reject cooked version");
     faset::player::SceneView view(folder);
+    lightingExtraction(view);
     physicsDebug(view);
     auto snapshot = view.build(scene, 16.f / 9.f);
     check(snapshot.draws.size() == 1, "SceneView builtin mesh");

tests/test_p3_lighting_benchmark.py

@@ -0,0 +1,229 @@
+"""Contract and arithmetic tests for the offline P3 lighting sweep wrapper."""
+
+import csv
+import json
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+SCRIPT = ROOT / "tools/benchmark_p3_lighting.py"
+sys.path.insert(0, str(ROOT / "tools"))
+
+
+def sample(shadows, visibility, lights, raster, gpu, repeat=1, frame=0):
+    return {
+        "shadows": shadows, "visibility": visibility, "light_count": str(lights),
+        "run_index": str(repeat), "frame": str(frame),
+        "gpu_main_raster_ms": str(raster), "gpu_ms": str(gpu),
+        "gpu_shadow_ms": "0", "cpu_ms": "1", "readback_cpu_ms": ".5",
+        "validation_errors": "0", "device": "Fake GPU", "driver": "Fake Driver",
+        "commit": "abc123", "effective_visibility": visibility,
+        "lighting_path": "forward", "submitted_local_lights": str(lights),
+        "omitted_local_lights": "0", "shadow_tiles": "0", "draw_calls": "1",
+        "gpu_bytes": "4096", "validation_enabled": "0", "width": "1920", "height": "1080",
+    }
+
+
+FAKE_BENCHMARK = r'''import argparse
+import csv
+import json
+from pathlib import Path
+
+p = argparse.ArgumentParser()
+for flag in ("lights", "run-index", "width", "height", "warmup", "frames"):
+    p.add_argument("--" + flag, type=int, required=True)
+for flag in ("shadows", "visibility", "csv", "commit", "validation"):
+    p.add_argument("--" + flag, required=True)
+p.add_argument("--driver")
+a = p.parse_args()
+path = Path(a.csv)
+path.with_suffix(".args.json").write_text(json.dumps(vars(a)), encoding="utf-8")
+fieldnames = ["light_count", "shadows", "visibility", "frame", "device", "driver",
+              "commit", "gpu_main_raster_ms", "gpu_ms", "gpu_shadow_ms", "cpu_ms",
+              "readback_cpu_ms", "validation_errors", "run_index", "effective_visibility",
+              "lighting_path", "submitted_local_lights", "omitted_local_lights",
+              "shadow_tiles", "draw_calls", "gpu_bytes", "validation_enabled", "width", "height"]
+with path.open("w", newline="", encoding="utf-8") as stream:
+    writer = csv.DictWriter(stream, fieldnames=fieldnames)
+    writer.writeheader()
+    for frame in range(a.frames):
+        writer.writerow(dict(light_count=a.lights, shadows=a.shadows,
+                             visibility=a.visibility, frame=frame, device="Fake GPU",
+                             driver="Fake Driver", commit=a.commit,
+                             gpu_main_raster_ms=.4 + .02 * a.lights, gpu_ms=4 + .02 * a.lights,
+                             gpu_shadow_ms=0, cpu_ms=1, readback_cpu_ms=.5,
+                             validation_errors=0, run_index=a.run_index,
+                             effective_visibility=a.visibility, lighting_path="forward",
+                             submitted_local_lights=a.lights, omitted_local_lights=0,
+                             shadow_tiles=0, draw_calls=1, gpu_bytes=4096,
+                             validation_enabled=0, width=a.width, height=a.height))
+'''
+
+
+class LightingBenchmarkTests(unittest.TestCase):
+    def test_list_runs_has_three_independent_repeats_for_each_shadow_setting(self):
+        process = subprocess.run([sys.executable, SCRIPT, "--list-runs"],
+                                 text=True, capture_output=True, check=True)
+        runs = json.loads(process.stdout)["runs"]
+        self.assertEqual(len(runs), 108)
+        for shadows in ("off", "on"):
+            group = [run for run in runs if run["shadows"] == shadows]
+            self.assertEqual(len(group), 54)
+            self.assertEqual({(run["light_count"], run["visibility"])
+                              for run in group},
+                             {(light, mode) for light in (0, 4, 16, 32, 64, 128)
+                              for mode in ("direct", "gpu-frustum", "gpu-occlusion")})
+            self.assertEqual({(run["light_count"], run["visibility"], run["repeat"])
+                              for run in group},
+                             {(light, mode, repeat)
+                              for light in (0, 4, 16, 32, 64, 128)
+                              for mode in ("direct", "gpu-frustum", "gpu-occlusion")
+                              for repeat in (1, 2, 3)})
+
+    def test_gate_uses_per_run_medians_and_same_mode_shadow_baseline(self):
+        from benchmark_p3_lighting import summarize_rows
+
+        rows = []
+        for repeat in (1, 2, 3):
+            for frame in (0, 1, 2):
+                rows.append(sample("off", "direct", 0, .5, 10, repeat, frame))
+                rows.append(sample("off", "direct", 32,
+                                   100 if repeat == 3 else 1.5, 11, repeat, frame))
+                rows.append(sample("on", "gpu-frustum", 0, .5, 4, repeat, frame))
+                rows.append(sample("on", "gpu-frustum", 64, 1.1, 4.6, repeat, frame))
+                rows.append(sample("off", "gpu-occlusion", 0, .5, 4, repeat, frame))
+                rows.append(sample("off", "gpu-occlusion", 128, 1.09, 4.59, repeat, frame))
+        summary = summarize_rows(rows)
+        hits = {(item["shadows"], item["visibility"], item["light_count"]): item
+                for item in summary["forward_plus_gate"]["candidates"]}
+        self.assertEqual(set(hits), {("off", "direct", 32),
+                                     ("on", "gpu-frustum", 64)})
+        self.assertAlmostEqual(hits[("off", "direct", 32)]["overhead_ms"], 1.0)
+        self.assertAlmostEqual(hits[("on", "gpu-frustum", 64)]["overhead_ms"], .6)
+        self.assertEqual(hits[("off", "direct", 32)]["zero_light_gpu_ms"], 10)
+        self.assertEqual(hits[("on", "gpu-frustum", 64)]["zero_light_gpu_ms"], 4)
+
+    def test_sweep_runs_fake_executable_and_preserves_all_raw_frames(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary)
+            fake = root / "fake_benchmark.py"
+            fake.write_text(FAKE_BENCHMARK, encoding="utf-8")
+            output = root / "café 世界"
+            process = subprocess.run(
+                [sys.executable, SCRIPT, "--sweep", "--executable", fake,
+                 "--output", output, "--shadows", "off", "--commit", "abc123",
+                 "--driver", "Fake Driver"],
+                text=True, capture_output=True)
+            self.assertEqual(process.returncode, 0, process.stderr)
+            raw = list((output / "raw").glob("*.csv"))
+            self.assertEqual(len(raw), 54)
+            with (output / "merged.csv").open(newline="", encoding="utf-8") as stream:
+                merged = list(csv.DictReader(stream))
+            self.assertEqual(len(merged), 54 * 30)
+            self.assertEqual({row["source_csv"] for row in merged},
+                             {path.name for path in raw})
+            report = json.loads((output / "summary.json").read_text(encoding="utf-8"))
+            self.assertEqual(report["runs_completed"], 54)
+            self.assertEqual(report["rows"], 54 * 30)
+            self.assertTrue(report["forward_plus_gate"]["triggered"])
+            one = json.loads(next((output / "raw").glob("*.args.json")).read_text())
+            self.assertEqual((one["width"], one["height"], one["warmup"], one["frames"]),
+                             (1920, 1080, 10, 30))
+            self.assertEqual(one["validation"], "off")
+
+    def test_sweep_rejects_missing_gpu_raster_column(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary)
+            fake = root / "bad_benchmark.py"
+            fake.write_text(FAKE_BENCHMARK.replace(
+                '"gpu_main_raster_ms", "gpu_ms"', '"gpu_ms"').replace(
+                'gpu_main_raster_ms=.4 + .02 * a.lights, ', ''), encoding="utf-8")
+            output = root / "invalid"
+            process = subprocess.run(
+                [sys.executable, SCRIPT, "--sweep", "--executable", fake,
+                 "--output", output, "--shadows", "off", "--commit", "abc123",
+                 "--driver", "Fake Driver"],
+                text=True, capture_output=True)
+            self.assertNotEqual(process.returncode, 0)
+            self.assertIn("gpu_main_raster_ms", process.stderr)
+            self.assertFalse((output / "summary.json").exists())
+
+    def test_sweep_rejects_visibility_fallback_as_a_mode_measurement(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary)
+            fake = root / "fallback.py"
+            fake.write_text(FAKE_BENCHMARK.replace(
+                'effective_visibility=a.visibility', 'effective_visibility="direct"'),
+                encoding="utf-8")
+            output = root / "fallback-output"
+            process = subprocess.run(
+                [sys.executable, SCRIPT, "--sweep", "--executable", fake,
+                 "--output", output, "--shadows", "off", "--commit", "abc123",
+                 "--driver", "Fake Driver"],
+                text=True, capture_output=True)
+            self.assertNotEqual(process.returncode, 0)
+            self.assertIn("effective_visibility", process.stderr)
+            self.assertFalse((output / "summary.json").exists())
+
+    def test_sweep_rejects_a_scene_that_does_not_submit_requested_lights(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary)
+            fake = root / "wrong-count.py"
+            fake.write_text(FAKE_BENCHMARK.replace(
+                'submitted_local_lights=a.lights', 'submitted_local_lights=0'),
+                encoding="utf-8")
+            output = root / "wrong-count-output"
+            process = subprocess.run(
+                [sys.executable, SCRIPT, "--sweep", "--executable", fake,
+                 "--output", output, "--shadows", "off", "--commit", "abc123",
+                 "--driver", "Fake Driver"],
+                text=True, capture_output=True)
+            self.assertNotEqual(process.returncode, 0)
+            self.assertIn("submitted_local_lights", process.stderr)
+            self.assertFalse((output / "summary.json").exists())
+
+    def test_sweep_requires_known_driver_identity(self):
+        from benchmark_p3_lighting import sweep
+        with tempfile.TemporaryDirectory() as temporary:
+            fake = Path(temporary) / "fake.py"
+            fake.write_text(FAKE_BENCHMARK, encoding="utf-8")
+            with self.assertRaisesRegex(ValueError, "--driver"):
+                sweep(fake, Path(temporary) / "out", "off", "abc123")
+
+
+def real_executable_smoke(executable: Path) -> None:
+    from benchmark_p3_lighting import REQUIRED_COLUMNS
+
+    choices = subprocess.run([executable, "--list-runs"], capture_output=True,
+                             text=True, check=True)
+    declared = json.loads(choices.stdout)
+    if declared["lights"] != [0, 4, 16, 32, 64, 128] or len(declared["visibility"]) != 3:
+        raise AssertionError("C++ executable and Python sweep matrix disagree")
+    with tempfile.TemporaryDirectory() as directory:
+        output = Path(directory) / "café 世界" / "smoke.csv"
+        subprocess.run([executable, "--lights", "4", "--shadows", "off",
+                        "--visibility", "direct", "--width", "64", "--height", "64",
+                        "--warmup", "0", "--frames", "1", "--validation", "on",
+                        "--commit", "smoke", "--driver", "smoke-driver",
+                        "--csv", output], capture_output=True, text=True, check=True)
+        with output.open(newline="", encoding="utf-8") as stream:
+            reader = csv.DictReader(stream)
+            columns, rows = reader.fieldnames or [], list(reader)
+        if set(REQUIRED_COLUMNS) - set(columns) or len(rows) != 1:
+            raise AssertionError("Real benchmark CSV lacks a complete single-frame row")
+        row = rows[0]
+        if (row["effective_visibility"] != "direct" or row["lighting_path"] != "forward" or
+                row["submitted_local_lights"] != "4" or row["validation_errors"] != "0" or
+                float(row["gpu_main_raster_ms"]) <= 0):
+            raise AssertionError("Real benchmark did not report the measured lighting path")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) == 3 and sys.argv[1] == "--real-executable":
+        real_executable_smoke(Path(sys.argv[2]).resolve())
+    else:
+        unittest.main()

tests/test_shader_reflection.py

@@ -36,6 +36,35 @@ def parameter(name: str, index: int, shape: str, access: str, stride: int | None
 
 
 class ReflectionTests(unittest.TestCase):
+    def test_graphics_lighting_abi(self):
+        compiler = os.environ["FASET_TEST_SLANGC"]
+        with tempfile.TemporaryDirectory(prefix="faset-lighting-abi-") as directory:
+            for source, entry, defines in (
+                ("baseline.slang", "fragmentMain", []),
+                ("gpu_scene.slang", "gpuVertexMain", ["--define", "FASET_GPU_GRAPHICS=1"]),
+            ):
+                process = subprocess.run(
+                    [sys.executable, str(SCRIPT), "--compiler", compiler, "--source",
+                     str(SCRIPT.parents[1] / "shaders" / source), "--entry", entry,
+                     *defines, "--output", directory],
+                    capture_output=True, text=True,
+                )
+                self.assertEqual(process.returncode, 0, process.stderr)
+            fragment = json.loads((Path(directory) / "fragmentMain.reflection.json").read_text())
+            gpu_vertex = json.loads((Path(directory) / "gpuVertexMain.reflection.json").read_text())
+            lighting = {
+                (d["set"], d["binding"]): (d["type"], d.get("element_stride"))
+                for d in fragment["layout"]["descriptors"]
+            }
+            self.assertEqual([lighting[1, i] for i in range(4)],
+                             [("storage_buffer", 80), ("storage_buffer", 80),
+                              ("storage_buffer", 112), ("sampled_image_2d", None)])
+            graphics = {
+                (d["set"], d["binding"]): d["element_stride"]
+                for d in gpu_vertex["layout"]["descriptors"]
+            }
+            self.assertEqual([graphics[2, i] for i in range(3)], [224, 4, 208])
+
     def test_gpu_vertex_paths_do_not_require_shader_draw_parameters(self):
         # SV_InstanceID makes Slang subtract BaseInstance and emit DrawParameters.
         # Our indirect commands always use firstInstance=0, so the Vulkan instance

tools/benchmark_p3_lighting.py

@@ -0,0 +1,262 @@
+#!/usr/bin/env python3
+"""Run the fixed P3 lighting sweep and retain raw per-frame GPU measurements.
+
+The Forward+ threshold in the summary is a measurement result, not an automatic
+renderer switch. Apply it to the Linux physical reference GPU; keep other devices
+as separate functional/performance observations.
+"""
+from __future__ import annotations
+
+import argparse
+import csv
+import json
+import math
+from pathlib import Path
+import statistics
+import subprocess
+import sys
+
+
+LIGHT_COUNTS = (0, 4, 16, 32, 64, 128)
+VISIBILITY_MODES = ("direct", "gpu-frustum", "gpu-occlusion")
+REPEATS = (1, 2, 3)
+WARMUP_FRAMES = 10
+MEASURED_FRAMES = 30
+WIDTH, HEIGHT = 1920, 1080
+REQUIRED_COLUMNS = (
+    "light_count", "shadows", "visibility", "frame", "device", "driver",
+    "commit", "gpu_main_raster_ms", "gpu_ms", "gpu_shadow_ms", "cpu_ms",
+    "readback_cpu_ms", "validation_errors", "run_index", "effective_visibility",
+    "lighting_path", "submitted_local_lights", "omitted_local_lights",
+    "shadow_tiles", "draw_calls", "gpu_bytes", "validation_enabled", "width", "height",
+)
+TIMING_COLUMNS = ("gpu_main_raster_ms", "gpu_ms", "gpu_shadow_ms", "cpu_ms",
+                  "readback_cpu_ms")
+
+
+def build_runs(shadows: str = "both") -> list[dict]:
+    if shadows not in ("off", "on", "both"):
+        raise ValueError(f"Unsupported shadow setting: {shadows}")
+    settings = ("off", "on") if shadows == "both" else (shadows,)
+    return [{"shadows": shadow, "visibility": mode, "light_count": lights,
+             "repeat": repeat}
+            for shadow in settings for mode in VISIBILITY_MODES
+            for lights in LIGHT_COUNTS for repeat in REPEATS]
+
+
+def median(values: list[float]) -> float:
+    if not values:
+        raise ValueError("Cannot summarize empty measurements")
+    return float(statistics.median(values))
+
+
+def p95(values: list[float]) -> float:
+    if not values:
+        raise ValueError("Cannot summarize empty measurements")
+    ordered = sorted(values)
+    return ordered[math.ceil(.95 * len(ordered)) - 1]
+
+
+def _measurement(row: dict, name: str) -> float:
+    try:
+        value = float(row[name])
+    except (KeyError, TypeError, ValueError) as error:
+        raise ValueError(f"Invalid {name} in benchmark CSV") from error
+    if not math.isfinite(value) or value < 0:
+        raise ValueError(f"Invalid {name} in benchmark CSV: {value}")
+    return value
+
+
+def summarize_rows(rows: list[dict]) -> dict:
+    """Use the median of each independent run's median, then compare like baselines."""
+    grouped: dict[tuple[str, str, int], dict[int, list[dict]]] = {}
+    for row in rows:
+        try:
+            key = (row["shadows"], row["visibility"], int(row["light_count"]))
+            repeat = int(row["run_index"])
+        except (KeyError, TypeError, ValueError) as error:
+            raise ValueError("Benchmark row lacks shadow/mode/light/repeat identity") from error
+        if key[0] not in ("off", "on") or key[1] not in VISIBILITY_MODES or repeat < 1:
+            raise ValueError(f"Invalid benchmark configuration: {key}, repeat {repeat}")
+        for name in TIMING_COLUMNS:
+            _measurement(row, name)
+        grouped.setdefault(key, {}).setdefault(repeat, []).append(row)
+
+    configurations = []
+    lookup = {}
+    for (shadows, visibility, lights), repeats in sorted(grouped.items()):
+        run_summaries = []
+        for repeat, samples in sorted(repeats.items()):
+            run_summaries.append({
+                "run_index": repeat, "frames": len(samples),
+                "median_ms": {name: median([_measurement(row, name) for row in samples])
+                              for name in TIMING_COLUMNS},
+            })
+        entry = {
+            "shadows": shadows, "visibility": visibility, "light_count": lights,
+            "runs": run_summaries,
+            "median_ms": {name: median([run["median_ms"][name] for run in run_summaries])
+                          for name in TIMING_COLUMNS},
+            "p95_ms": {name: p95([_measurement(row, name) for samples in repeats.values()
+                                   for row in samples]) for name in TIMING_COLUMNS},
+        }
+        configurations.append(entry)
+        lookup[(shadows, visibility, lights)] = entry
+
+    candidates = []
+    evaluated = []
+    for entry in configurations:
+        if entry["light_count"] not in (32, 64, 128):
+            continue
+        baseline = lookup.get((entry["shadows"], entry["visibility"], 0))
+        if baseline is None:
+            raise ValueError("Forward+ gate requires a zero-light baseline for each mode/shadow setting")
+        zero_gpu = baseline["median_ms"]["gpu_ms"]
+        if zero_gpu <= 0:
+            raise ValueError("Forward+ gate requires positive zero-light GPU frame timing")
+        overhead = (entry["median_ms"]["gpu_main_raster_ms"] -
+                    baseline["median_ms"]["gpu_main_raster_ms"])
+        result = {"shadows": entry["shadows"], "visibility": entry["visibility"],
+                  "light_count": entry["light_count"], "overhead_ms": overhead,
+                  "zero_light_gpu_ms": zero_gpu,
+                  "overhead_percent_of_zero_gpu": 100 * overhead / zero_gpu,
+                  "absolute_threshold_reached": overhead >= 1.0,
+                  "relative_threshold_reached": overhead >= .15 * zero_gpu}
+        evaluated.append(result)
+        if result["absolute_threshold_reached"] or result["relative_threshold_reached"]:
+            candidates.append(result)
+    return {"configurations": configurations,
+            "forward_plus_gate": {"triggered": bool(candidates), "candidates": candidates,
+                                  "evaluated": evaluated,
+                                  "basis": "median of three independent run medians; same-mode/shadow zero-light GPU baseline"}}
+
+
+def _read_run_csv(path: Path, run: dict, commit: str) -> tuple[list[str], list[dict]]:
+    with path.open(newline="", encoding="utf-8") as stream:
+        reader = csv.DictReader(stream)
+        columns = reader.fieldnames or []
+        missing = sorted(set(REQUIRED_COLUMNS) - set(columns))
+        if missing:
+            raise ValueError(f"{path}: missing CSV column(s): {', '.join(missing)}")
+        rows = list(reader)
+    if len(rows) != MEASURED_FRAMES:
+        raise ValueError(f"{path}: expected {MEASURED_FRAMES} measured frames, got {len(rows)}")
+    frames = set()
+    for row in rows:
+        expected = {"light_count": str(run["light_count"]), "shadows": run["shadows"],
+                    "visibility": run["visibility"], "run_index": str(run["repeat"]),
+                    "commit": commit, "width": str(WIDTH), "height": str(HEIGHT)}
+        for name, value in expected.items():
+            if row[name] != value:
+                raise ValueError(f"{path}: {name} mismatch: expected {value}, got {row[name]}")
+        if row["effective_visibility"] != run["visibility"]:
+            raise ValueError(f"{path}: effective_visibility fell back from {run['visibility']}")
+        if row["submitted_local_lights"] != str(run["light_count"]) or row["omitted_local_lights"] != "0":
+            raise ValueError(f"{path}: submitted_local_lights or omitted_local_lights disagrees with the workload")
+        try:
+            frame = int(row["frame"])
+            errors = int(row["validation_errors"])
+        except ValueError as error:
+            raise ValueError(f"{path}: invalid frame or validation error count") from error
+        if frame in frames or errors != 0:
+            raise ValueError(f"{path}: duplicate frame or Vulkan validation error")
+        frames.add(frame)
+        if not row["device"] or not row["driver"] or not row["lighting_path"]:
+            raise ValueError(f"{path}: device, driver and effective lighting path are required")
+        for name in TIMING_COLUMNS:
+            _measurement(row, name)
+    return columns, rows
+
+
+def _git_revision() -> str:
+    root = Path(__file__).resolve().parents[1]
+    return subprocess.check_output(["git", "-C", str(root), "rev-parse", "HEAD"],
+                                   text=True).strip()
+
+
+def sweep(executable: Path, output: Path, shadows: str, commit: str,
+          validation: str = "off", driver: str | None = None) -> dict:
+    if not executable.is_file():
+        raise ValueError(f"Benchmark executable does not exist: {executable}")
+    if driver is None or not driver.strip() or driver.strip().lower() == "unknown":
+        raise ValueError("A measured sweep requires an explicit --driver identity")
+    if output.exists() and any(output.iterdir()):
+        raise ValueError(f"Output directory must be new or empty: {output}")
+    raw = output / "raw"
+    raw.mkdir(parents=True)
+    all_rows = []
+    columns = None
+    runs = build_runs(shadows)
+    command_prefix = [sys.executable, str(executable)] if executable.suffix.lower() == ".py" else [str(executable)]
+    for run in runs:
+        filename = (f"shadows-{run['shadows']}_{run['visibility']}_"
+                    f"lights-{run['light_count']:03d}_run-{run['repeat']}.csv")
+        target = raw / filename
+        command = command_prefix + [
+            "--lights", str(run["light_count"]), "--shadows", run["shadows"],
+            "--visibility", run["visibility"], "--csv", str(target),
+            "--run-index", str(run["repeat"]), "--commit", commit,
+            "--validation", validation, "--width", str(WIDTH), "--height", str(HEIGHT),
+            "--warmup", str(WARMUP_FRAMES), "--frames", str(MEASURED_FRAMES),
+        ]
+        if driver is not None:
+            command += ["--driver", driver]
+        result = subprocess.run(command, capture_output=True, text=True, encoding="utf-8",
+                                errors="replace", timeout=180)
+        if result.returncode != 0:
+            raise RuntimeError(f"Benchmark failed for {filename}: {result.stderr[-2000:]}")
+        run_columns, samples = _read_run_csv(target, run, commit)
+        if columns is None:
+            columns = run_columns
+        elif columns != run_columns:
+            raise ValueError(f"{target}: CSV schema differs from other runs")
+        all_rows.extend({**row, "source_csv": filename} for row in samples)
+
+    merged = output / "merged.csv"
+    with merged.open("w", newline="", encoding="utf-8") as stream:
+        writer = csv.DictWriter(stream, fieldnames=[*(columns or []), "source_csv"])
+        writer.writeheader()
+        writer.writerows(all_rows)
+    summary = {"format": "faset.p3-lighting-benchmark", "version": 1,
+               "commit": commit, "warmup_frames_per_run": WARMUP_FRAMES,
+               "measured_frames_per_run": MEASURED_FRAMES, "width": WIDTH, "height": HEIGHT,
+               "validation": validation, "driver": driver,
+               "runs_completed": len(runs), "rows": len(all_rows),
+               **summarize_rows(all_rows)}
+    (output / "summary.json").write_text(json.dumps(summary, indent=2) + "\n",
+                                          encoding="utf-8")
+    return summary
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    mode = parser.add_mutually_exclusive_group(required=True)
+    mode.add_argument("--list-runs", action="store_true", help="Print the deterministic sweep matrix as JSON")
+    mode.add_argument("--sweep", action="store_true", help="Run every configuration and retain raw CSV")
+    parser.add_argument("--shadows", choices=("off", "on", "both"), default="both")
+    parser.add_argument("--executable", type=Path, help="Built C++ benchmark executable")
+    parser.add_argument("--output", type=Path, help="New or empty evidence directory")
+    parser.add_argument("--commit", help="Source revision; defaults to this checkout's HEAD")
+    parser.add_argument("--driver", help="Required driver identity for a measured sweep")
+    parser.add_argument("--validation", choices=("on", "off"), default="off")
+    args = parser.parse_args()
+    if args.list_runs:
+        print(json.dumps({"format": "faset.p3-lighting-run-matrix", "version": 1,
+                          "runs": build_runs(args.shadows)}, indent=2))
+        return 0
+    if args.executable is None or args.output is None:
+        parser.error("--sweep requires --executable and --output")
+    try:
+        summary = sweep(args.executable.resolve(), args.output.resolve(), args.shadows,
+                        args.commit or _git_revision(), args.validation, args.driver)
+    except (OSError, ValueError, RuntimeError) as error:
+        print(f"P3 lighting benchmark failed: {error}", file=sys.stderr)
+        return 1
+    print(json.dumps({"summary": str(args.output.resolve() / "summary.json"),
+                      "runs_completed": summary["runs_completed"],
+                      "forward_plus_threshold_reached": summary["forward_plus_gate"]["triggered"]}))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())