Initial commit: Minecraft 光追着色器包（从零实现的 path tracing）

shaders/Lib/RTWSM/BackwardAnalysis.glsl

@@ -0,0 +1,45 @@
+// MinecraftPT — RTWSM Backward Analysis
+// Computes the importance map from the shadow map depth: which shadow map texels
+// need more resolution (near-field geometry, steep normals).
+
+#include "/Lib/Settings.glsl"
+#include "/Lib/Utilities.glsl"
+#include "/Lib/PathTracing/Voxelizer/VoxelProfile.glsl"
+
+const ivec3 workGroups = ivec3(32, 16, 1);
+layout (local_size_x = 32, local_size_y = 32) in;
+
+layout (r32f) uniform writeonly image2D img_rtwImportance2D;
+
+uniform sampler2D shadowcolor0;
+
+void main(){
+	ivec2 texel = ivec2(gl_GlobalInvocationID.xy);
+	vec2 uv = (vec2(texel) + 0.5) / vec2(RTW_RESOLUTION, RTW_RESOLUTION_Y);
+
+	// Sample shadow map depth (in the shadow region)
+	vec2 shadowUv = vec2(uv.x * 0.5 + 0.5, uv.y * 0.5); // map to right region
+	vec2 shadowTexel = shadowUv * shadowSize;
+
+	vec4 shadowData = texelFetch(shadowcolor0, ivec2(shadowTexel), 0);
+
+	float depth = shadowData.a;
+	float importance = 0.0;
+
+	if (depth < 1.0){
+		// Depth-based importance: closer = more important
+		float dist = 1.0 - depth;
+		importance = pow(dist, 2.0) * RTW_BACKWARD_DIST_FACTOR;
+
+		// Depth gradient importance (edges)
+		float dLeft = texelFetch(shadowcolor0, ivec2(shadowTexel) + ivec2(-1, 0), 0).a;
+		float dRight = texelFetch(shadowcolor0, ivec2(shadowTexel) + ivec2(1, 0), 0).a;
+		float dUp = texelFetch(shadowcolor0, ivec2(shadowTexel) + ivec2(0, -1), 0).a;
+		float dDown = texelFetch(shadowcolor0, ivec2(shadowTexel) + ivec2(0, 1), 0).a;
+
+		float gradient = abs(dLeft - dRight) + abs(dUp - dDown);
+		importance += gradient * 0.5 * RTW_BACKWARD_NORMAL_FACTOR;
+	}
+
+	imageStore(img_rtwImportance2D, texel, vec4(importance));
+}