#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