fix: restore MemoryCopy for UBO + PBR shader with point light

- UBO packing: MemoryCopy for vp (64B) + lightPos (16B) + lightColor (16B)
- PBR fragment shader with Cook-Torrance BRDF + point light
- No directional light, near-zero ambient — only point light illuminates
- Guards against div-by-zero in attenuation and specular
- Depth buffer properly configured in pipeline + rendering info

src/Engine.Graphics.Vulkan/Shaders/triangle.frag

@@ -12,13 +12,91 @@ layout(set = 0, binding = 0) uniform CameraUBO {
     vec4 pointLightColor;
 };
 
+const vec3 AMBIENT = vec3(0.01, 0.01, 0.02);
+const float PI = 3.14159265359;
+
+float distributionGGX(vec3 N, vec3 H, float roughness)
+{
+    float a = roughness * roughness;
+    float a2 = a * a;
+    float NdotH = max(dot(N, H), 0.0);
+    float NdotH2 = NdotH * NdotH;
+    float num = a2;
+    float denom = NdotH2 * (a2 - 1.0) + 1.0;
+    denom = PI * denom * denom;
+    return num / denom;
+}
+
+float geometrySchlickGGX(float NdotV, float roughness)
+{
+    float r = roughness + 1.0;
+    float k = (r * r) / 8.0;
+    return NdotV / (NdotV * (1.0 - k) + k);
+}
+
+float geometrySmith(vec3 N, vec3 V, vec3 L, float roughness)
+{
+    float NdotV = max(dot(N, V), 0.0);
+    float NdotL = max(dot(N, L), 0.0);
+    return geometrySchlickGGX(NdotV, roughness) * geometrySchlickGGX(NdotL, roughness);
+}
+
+vec3 fresnelSchlick(float cosTheta, vec3 F0)
+{
+    return F0 + (1.0 - F0) * pow(clamp(1.0 - cosTheta, 0.0, 1.0), 5.0);
+}
+
+vec3 acesTonemap(vec3 color)
+{
+    float a = 2.51;
+    float b = 0.03;
+    float c = 2.43;
+    float d = 0.59;
+    float e = 0.14;
+    return clamp((color * (a * color + b)) / (color * (c * color + d) + e), 0.0, 1.0);
+}
+
 void main()
 {
-    // Debug: just output the light position as color
-    vec3 lp = pointLightPos.xyz;
-    float intensity = pointLightPos.w;
-    
-    // Map position to visible range
-    vec3 debugColor = lp * 0.1 + vec3(0.5);
-    outColor = vec4(debugColor * fragAlbedo, 1.0);
+    vec3 N = normalize(fragNormal);
+    vec3 V = normalize(-fragWorldPos);
+    vec3 albedo = fragAlbedo;
+    float roughness = 0.5;
+    float metallic = 0.1;
+
+    vec3 color = AMBIENT * albedo;
+
+    vec3 lightPos = pointLightPos.xyz;
+    float lightIntensity = pointLightPos.w;
+    vec3 lightColor = pointLightColor.xyz;
+    float lightRange = pointLightColor.w;
+
+    vec3 toLight = lightPos - fragWorldPos;
+    float dist = length(toLight);
+    vec3 L = toLight / max(dist, 0.001);
+
+    float attenuation = pow(clamp(1.0 - dist / max(lightRange, 0.001), 0.0, 1.0), 2.0);
+    vec3 radiance = lightColor * lightIntensity * attenuation;
+
+    vec3 H = normalize(V + L);
+    vec3 F0 = mix(vec3(0.04), albedo, metallic);
+
+    float NDF = distributionGGX(N, H, roughness);
+    float G = geometrySmith(N, V, L, roughness);
+    vec3 F = fresnelSchlick(max(dot(H, V), 0.0), F0);
+
+    vec3 numerator = NDF * G * F;
+    float denominator = 4.0 * max(dot(N, V), 0.0) * max(dot(N, L), 0.0) + 0.0001;
+    vec3 specular = numerator / denominator;
+
+    vec3 kS = F;
+    vec3 kD = (vec3(1.0) - kS) * (1.0 - metallic);
+
+    float NdotL = max(dot(N, L), 0.0);
+    color += (kD * albedo / PI + specular) * radiance * NdotL;
+
+    color = acesTonemap(color);
+    color = pow(color, vec3(1.0 / 2.2));
+
+    outColor = vec4(color, 1.0);
 }

src/Engine.Graphics.Vulkan/VulkanRenderer.cs

@@ -102,13 +102,12 @@ internal sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreen
 
         // Pack UBO: mat4 vp (64 bytes) + vec4 lightPos (16) + vec4 lightColor (16) = 96 bytes
         var uboData = stackalloc byte[128];
-        var pFloat = (float*)uboData;
-        pFloat[0] = vp.M11; pFloat[1] = vp.M12; pFloat[2] = vp.M13; pFloat[3] = vp.M14;
-        pFloat[4] = vp.M21; pFloat[5] = vp.M22; pFloat[6] = vp.M23; pFloat[7] = vp.M24;
-        pFloat[8] = vp.M31; pFloat[9] = vp.M32; pFloat[10] = vp.M33; pFloat[11] = vp.M34;
-        pFloat[12] = vp.M41; pFloat[13] = vp.M42; pFloat[14] = vp.M43; pFloat[15] = vp.M44;
-        pFloat[16] = lightPos.X; pFloat[17] = lightPos.Y; pFloat[18] = lightPos.Z; pFloat[19] = lightPos.W;
-        pFloat[20] = lightColor.X; pFloat[21] = lightColor.Y; pFloat[22] = lightColor.Z; pFloat[23] = lightColor.W;
+        var vpCopy = vp;
+        System.Buffer.MemoryCopy(&vpCopy, uboData, 64, 64);
+        var lpCopy = lightPos;
+        System.Buffer.MemoryCopy(&lpCopy, uboData + 64, 16, 16);
+        var lcCopy = lightColor;
+        System.Buffer.MemoryCopy(&lcCopy, uboData + 80, 16, 16);
 
         var drawCalls = new List<(VkBuffer vertexBuf, VkBuffer indexBuf, uint indexCount, Matrix4x4 model)>();