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

shaders/Lib/IndividualFunctions/PlanarClouds.glsl

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+#include "/Lib/Settings.glsl"
+#include "/Lib/Utilities.glsl"
+#include "/Lib/BasicFunctions/LightingConstants.glsl"
+// MinecraftPT — Planar Clouds
+// Simple 2D cloud layer rendered as a plane at altitude.
+
+#ifndef PLANAR_CLOUDS_GLSL
+#define PLANAR_CLOUDS_GLSL
+
+// Sample cloud density at a world XZ position (2D noise + coverage)
+float GetPlanarCloudDensity(vec2 xz, float time, out vec3 cloudColor){
+	// Coverage by weather
+	float coverage = mix(PC_CLEAR_COVERAGE, PC_RAIN_COVERAGE, wetness);
+	float density = mix(PC_CLEAR_DENSITY, PC_RAIN_DENSITY, wetness);
+	float sunlighting = mix(PC_CLEAR_SUNLIGHTING, PC_RAIN_SUNLIGHTING, wetness);
+	float skylighting = mix(PC_CLEAR_SKYLIGHTING, PC_RAIN_SKYLIGHTING, wetness);
+
+	// FBM noise
+	vec2 p = xz * PC_NOISE_SCALE + vec2(time * 0.01, 0.0);
+	float n = 0.0;
+	float amp = 0.5;
+	for (int i = 0; i < 3; i++){
+		n += textureLod(CloudNoise3D, vec3(p, 0.5), 0.0).r * amp;
+		p *= 2.0;
+		amp *= 0.5;
+	}
+
+	float clouds = saturate((n - (1.0 - coverage)) * (1.0 / max(coverage, 0.01)));
+
+	// Cloud color: lit by sun and sky
+	float sunFactor = sunlighting;
+	cloudColor = mix(GetCloudAtmoIrradiance(), GetCloudSunIrradiance(), sunFactor) * clouds
+		+ vec3(1.0) * skylighting * clouds;
+
+	return clouds * density;
+}
+
+#endif