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Render stable cascaded sun shadows into a bounded atlas

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Emil
2026-09-24 02:37:42 +03:00
parent 36a44e14ca
commit 252f7e2e91
5 changed files with 380 additions and 67 deletions
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shaders/baseline.slang
+44 -10
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@@ -27,7 +27,7 @@ struct FrameParameters {
// 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
uint4 counts; // local count, sun enabled, sun shadow enabled, sun view count
float4 sunDirectionIntensity; // xyz world-space ray direction, w intensity
float4 sunColor;
float4 cameraForwardShadowDistance;
@@ -58,6 +58,26 @@ VertexOutput vertexMain(VertexInput v) {
}
[shader("vertex")]
float4 shadowMain(VertexInput v) : SV_Position { return mul(frame.lightViewProjection, float4(v.world,1)); }
float sampleSunCascade(uint index, float3 world, float nl) {
ShadowViewGpu record = shadowViews[index];
if (record.biasFlags.w < 0.5) return 1.0;
float4 clip = mul(record.viewProjection, float4(world,1));
if (clip.w <= 0.0) return 1.0;
float3 projected = clip.xyz / clip.w;
float2 localUV = projected.xy * 0.5 + 0.5;
if (any(localUV < 0.0) || any(localUV > 1.0) ||
projected.z < 0.0 || projected.z > 1.0) return 1.0;
float2 atlasUV = localUV * record.tileScaleOffset.xy + record.tileScaleOffset.zw;
float bias = max(record.biasFlags.x, record.biasFlags.y * (1.0 - nl));
float visible = 0.0;
for (int y=-1; y<=1; ++y) for (int x=-1; x<=1; ++x) {
float2 tap = clamp(atlasUV + float2(x,y) * record.biasFlags.z,
record.guardedClamp.xy, record.guardedClamp.zw);
float depth = shadowMap.SampleLevel(shadowSampler, tap, 0);
visible += projected.z - bias <= depth ? 1.0 / 9.0 : 0.0;
}
return visible;
}
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);
@@ -94,15 +114,29 @@ float4 fragmentMain(VertexOutput v) : SV_Target {
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;
if (lighting.counts.z != 0 && lighting.counts.w != 0 && nl > 0) {
if (lighting.counts.w == 1) {
visibility = sampleSunCascade(0, v.world, nl);
} else {
float cameraDepth = dot(v.world - frame.eye.xyz,
lighting.cameraForwardShadowDistance.xyz);
if (cameraDepth >= 0.0 &&
cameraDepth <= lighting.cameraForwardShadowDistance.w) {
uint cascade = 0;
while (cascade + 1 < lighting.counts.w &&
cameraDepth > lighting.cascadeSplits[cascade]) ++cascade;
visibility = sampleSunCascade(cascade, v.world, nl);
if (cascade + 1 < lighting.counts.w) {
float previousSplit = cascade == 0 ? 0.0 :
lighting.cascadeSplits[cascade-1];
float blendWidth = max(0.2,
0.1 * (lighting.cascadeSplits[cascade] - previousSplit));
float blend = saturate((cameraDepth -
(lighting.cascadeSplits[cascade] - blendWidth)) / blendWidth);
if (blend > 0.0)
visibility = lerp(visibility,
sampleSunCascade(cascade+1, v.world, nl), blend);
}
}
}
}