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

shaders/Lib/IndividualFunctions/VolumetricFog.glsl

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+#include "/Lib/BasicFunctions/LightingConstants.glsl"
+// MinecraftPT — Volumetric Fog
+// Height-based volumetric fog with 3D noise, ray marched in the volumetric pass.
+
+#ifndef VOLUMETRIC_FOG_GLSL
+uniform sampler3D CloudNoise3D;
+#define VOLUMETRIC_FOG_GLSL
+
+// Fog density at a world position (height + noise)
+float GetVolumetricFogDensity(vec3 worldPos, float time){
+	float height = worldPos.y;
+
+	// Two-layer height fog
+	float density = VFOG_DENSITY_BASE;
+	density += exp(-(height - VFOG_HEIGHT) * VFOG_FALLOFF) * VFOG_DENSITY;
+	density += exp(-(height - VFOG_HEIGHT_2) * VFOG_FALLOFF * 2.0) * VFOG_DENSITY * 0.5;
+
+	// Noise variation
+	#ifdef VFOG_NOISE_TYPE
+		if (VFOG_NOISE_TYPE > 0){
+			vec3 p = worldPos * vec3(VFOG_NOISE_HORIZONTAL_SCALE, VFOG_NOISE_VERTICAL_SCALE, VFOG_NOISE_HORIZONTAL_SCALE) + vec3(time * 0.01, 0.0, time * 0.008);
+			float n = 0.0;
+			float amp = 0.5;
+			for (int i = 0; i < VFOG_NOISE_OCTAVE; i++){
+				n += textureLod(CloudNoise3D, fract(p), 0.0).r * amp;
+				p *= 2.0;
+				amp *= 0.5;
+			}
+			density *= 1.0 + (n - 0.5) * VFOG_NOISE_COVERAGE * 2.0;
+		}
+	#endif
+
+	// Rain fog boost
+	density *= 1.0 + wetness * VFOG_RAIN_DENSITY_MUL;
+
+	return max(density, 0.0);
+}
+
+// In-scattering color for fog (sun + sky)
+vec3 GetFogColor(vec3 worldPos, vec3 sunDir){
+	vec3 sunColor = GetSunIrradiance() * VFOG_SUNLIGHT_DENSITY;
+	vec3 skyColor = GetAtmoIrradiance();
+
+	return skyColor + sunColor * 0.5;
+}
+
+#endif