// MinecraftPT — IRC_CS (Irradiance Cache Update)
// Updates the 3D irradiance cache: traces a few rays per cell toward the sky,
// stores ambient + direct light contributions, blends over time.

#include "/Lib/Settings.glsl"
#include "/Lib/Utilities.glsl"
#include "/Lib/BasicFunctions/LightingConstants.glsl"
#include "/Lib/PathTracing/Voxelizer/VoxelProfile.glsl"
#include "/Lib/PathTracing/Tracer/ShadowTracing.glsl"
#include "/Lib/BasicFunctions/PrecomputedAtmosphere.glsl"

#ifdef PT_IRC


const ivec3 workGroups = ivec3(int(ceil(float(ircResolution) / 4.0)));
layout (local_size_x = 4, local_size_y = 4, local_size_z = 4) in;

layout (rgba16f) uniform writeonly image3D img_irradianceCache3D;
layout (rgba16f) uniform readonly image3D img_irradianceCache3D_Alt;

uniform sampler3D voxelData3D;

void main(){
	ivec3 texel = ivec3(gl_GlobalInvocationID.xyz);

	if (any(greaterThanEqual(texel, ivec3(ircResolution)))){
		return;
	}

	// World position of this cache cell
	vec3 cellPos = (vec3(texel) + 0.5) / float(ircResolution);
	vec3 worldPos = (cellPos - 0.5) * voxelDistance + cameraPosition;

	// Voxel occupancy check — don't cache inside solid blocks
	vec3 voxelCoord = cellPos * voxelResolution;
	vec4 voxelData = texelFetch(voxelData3D, ivec3(clamp(voxelCoord, vec3(0.0), vec3(voxelResolution - 1.0))), 0);
	float voxelID = DecodeVoxelID(voxelData.z);

	if (voxelID > 1.0 && voxelID < 999.0){
		// Solid — keep old value
		return;
	}

	// Sample sky irradiance from multiple directions (hemisphere)
	vec3 irradiance = vec3(0.0);

	for (int i = 0; i < PT_IRC_SPP; i++){
		// Deterministic sample directions over hemisphere
		float phi = 6.28318 * hash1(vec3(texel) + float(i) * 1.7);
		float cosTheta = hash1(vec3(texel) * 2.0 + float(i) * 3.1);
		float sinTheta = sqrt(1.0 - cosTheta * cosTheta);

		vec3 dir = vec3(cos(phi) * sinTheta, cosTheta, sin(phi) * sinTheta);

		// Trace toward sky — if not blocked, add sky light
		vec3 voxelPos = WorldToVoxel(worldPos) + dir * 0.5;
		float visibility = SimpleShadowTracing(voxelPos, dir);

		// Sky radiance in this direction (analytic)
		vec3 skyRadiance = GetSkyRadiance(dir, GetSunDirWorld());

		irradiance += skyRadiance * visibility;
	}

	irradiance /= float(PT_IRC_SPP);

	// Sun contribution (direct)
	vec3 sunDir = GetSunDirWorld();
	float sunVis = SimpleShadowTracing(WorldToVoxel(worldPos), sunDir);
	irradiance += GetSunIrradiance() * sunVis * max(sunDir.y, 0.0);

	// Blend with previous (temporal smoothing), ping-pong by frame parity
	bool evenFrame = (frameCounter % 2) == 0;
	vec3 prev = evenFrame
		? texelFetch(img_irradianceCache3D_Alt, texel, 0).rgb
		: texelFetch(img_irradianceCache3D, texel, 0).rgb;
	irradiance = mix(prev, irradiance, PT_IRC_BLENDWEIGHT);

	if (evenFrame){
		imageStore(img_irradianceCache3D, texel, vec4(irradiance, 1.0));
	}else{
		imageStore(img_irradianceCache3D_Alt, texel, vec4(irradiance, 1.0));
	}
}

#endif