// MinecraftPT — Volumetric_FS
// Volumetric fog + volumetric clouds ray marched per-pixel and composited.

#include "/Lib/Settings.glsl"
#include "/Lib/Utilities.glsl"
#include "/Lib/BasicFunctions/LightingConstants.glsl"
#include "/Lib/BasicFunctions/TemporalNoise.glsl"
#include "/Lib/IndividualFunctions/VolumetricFog.glsl"
#include "/Lib/IndividualFunctions/WaterFog.glsl"
#include "/Lib/IndividualFunctions/PlanarClouds.glsl"
#include "/Lib/IndividualFunctions/CloudShadow.glsl"

uniform sampler2D colortex12; // HDR scene

layout(location = 0) out vec4 colorOut;

void main(){
	vec2 texelCoord = gl_FragCoord.xy;
	vec3 sceneColor = texelFetch(colortex12, ivec2(texelCoord), 0).rgb;

	float depth = texelFetch(depthtex0, ivec2(texelCoord), 0).r;

	// Reconstruct view position
	vec4 viewPos = gbufferProjectionInverse * vec4(texelCoord / screenSize * 2.0 - 1.0, depth * 2.0 - 1.0, 1.0);
	viewPos.xyz /= viewPos.w;

	vec3 worldPos = gbufferModelViewInverse[3].xyz + viewPos.xyz;

	// Dithering for the ray march
	float dither = BlueNoiseTemporal();

	// Volumetric fog accumulation
	vec3 fogColor = vec3(0.0);
	float transmittance = 1.0;

	// Ray march toward the surface
	int steps = VFOG_QUALITY;
	float dist = length(viewPos.xyz);
	float stepSize = dist / float(steps);

	vec3 rayDir = normalize(viewPos.xyz);
	vec3 marchPos = worldPos;

	float time = frameTimeCounter * 0.05;

	for (int i = 0; i < steps; i++){
		float t = (float(i) + dither) * stepSize;
		vec3 samplePos = marchPos - rayDir * t;

		float density = GetVolumetricFogDensity(samplePos, time);
		density *= stepSize;

		// Sun scattering
		float phase = 0.5 + 0.5 * dot(normalize(GetSunDirWorld()), -rayDir);

		vec3 inscatter = GetFogColor(samplePos, GetSunDirWorld()) * density * phase;

		fogColor += transmittance * inscatter;
		transmittance *= exp(-density);
	}

	// Cloud shadow on fog
	#ifdef VFOG_CLOUD_SHADOW
		float cloudShadow = GetCloudShadow(worldPos);
		fogColor *= cloudShadow;
	#endif

	// Combine
	vec3 finalColor = sceneColor * transmittance + fogColor;

	// Water fog (underwater)
	#ifdef UNDERWATER_VFOG
		if (isEyeInWater > 0){
			vec3 waterColor = GetWaterFogColor(worldPos);
			float waterFog = 1.0 - exp(-dist * GetWaterFogDensity(worldPos) * UNDERWATER_VFOG_DENSITY);
			finalColor = mix(finalColor, waterColor * 3.0, waterFog);
		}
	#endif

	colorOut = vec4(finalColor, 1.0);
}