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

shaders/Lib/BasicFunctions/HeldLight.glsl

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+// MinecraftPT — Held Light
+// Torch in hand / flashlight illumination.
+
+#ifndef HELDLIGHT_GLSL
+#define HELDLIGHT_GLSL
+
+// Physical held light: torches held in hand or flashlight
+vec3 GetHeldLight(vec3 worldPos, vec3 worldNormal, out float heldLightShadow){
+	vec3 result = vec3(0.0);
+	heldLightShadow = 1.0;
+
+	#ifdef HELDLIGHT_MODE
+		#if HELDLIGHT_MODE >= 1
+			// Torch in hand position (roughly 0.4, -0.4, 0.6 relative to camera)
+			vec3 heldPos = gbufferModelViewInverse[3].xyz + cameraPosition;
+			vec3 toLight = heldPos - worldPos;
+			float dist = length(toLight);
+			vec3 dir = toLight / max(dist, 1e-4);
+
+			float intensity = exp(-dist * dist * HELDLIGHT_FALLOFF) * HELDLIGHT_BRIGHTNESS;
+			float NdotL = max(dot(worldNormal, dir), 0.0);
+
+			vec3 color = pow(vec3(COLOR_TORCH_R, COLOR_TORCH_G, COLOR_TORCH_B), vec3(2.2));
+
+			result = color * intensity * NdotL;
+
+			#ifdef HELDLIGHT_SHADOW
+				// Simple ray shadow for held light (short distance)
+				heldLightShadow = SimpleShadowTracing(WorldToVoxel(worldPos + worldNormal * 0.1), dir);
+			#endif
+		#endif
+	#endif
+
+	return result;
+}
+
+#endif