#ifndef _CONETRACE_GLSL_
#define _CONETRACE_GLSL_

// References
// https://github.com/Friduric/voxel-cone-tracing
// https://github.com/Cigg/Voxel-Cone-Tracing
// https://github.com/GreatBlambo/voxel_cone_tracing/
// http://simonstechblog.blogspot.com/2013/01/implementing-voxel-cone-tracing.html
// http://leifnode.com/2015/05/voxel-cone-traced-global-illumination/
// http://www.seas.upenn.edu/%7Epcozzi/OpenGLInsights/OpenGLInsights-SparseVoxelization.pdf
// https://research.nvidia.com/sites/default/files/publications/GIVoxels-pg2011-authors.pdf

const float MAX_DISTANCE = 1.73205080757 * voxelgiRange;
const float VOXEL_SIZE = (2.0 / voxelgiResolution.x) * voxelgiStep;

// uniform sampler3D voxels;
// uniform sampler3D voxelsLast;

// vec3 orthogonal(const vec3 u) {
// 	// Pass normalized u
// 	const vec3 v = vec3(0.99146, 0.11664, 0.05832); // Pick any normalized vector
// 	return abs(dot(u, v)) > 0.99999 ? cross(u, vec3(0.0, 1.0, 0.0)) : cross(u, v);
// }

vec3 tangent(const vec3 n) {
	vec3 t1 = cross(n, vec3(0, 0, 1));
	vec3 t2 = cross(n, vec3(0, 1, 0));
	if (length(t1) > length(t2)) return normalize(t1);
	else return normalize(t2);
}

float traceConeAO(sampler3D voxels, const vec3 origin, vec3 dir, const float aperture, const float maxDist) {
	dir = normalize(dir);
	float sampleCol = 0.0;
	float dist = 1.5 * VOXEL_SIZE * voxelgiOffset;
	float diam = dist * aperture;
	vec3 samplePos;
	while (sampleCol < 1.0 && dist < maxDist) {
		samplePos = dir * dist + origin;
		float mip = max(log2(diam * voxelgiResolution.x), 0);
		float mipSample = textureLod(voxels, samplePos * 0.5 + vec3(0.5), mip).r;
		sampleCol += (1 - sampleCol) * mipSample;
		dist += max(diam / 2, VOXEL_SIZE);
		diam = dist * aperture;
	}
	return sampleCol;
}

float traceConeAOShadow(sampler3D voxels, const vec3 origin, vec3 dir, const float aperture, const float maxDist, const float offset) {
	dir = normalize(dir);
	float sampleCol = 0.0;
	float dist = 1.5 * VOXEL_SIZE * voxelgiOffset * 2.5; //
	float diam = dist * aperture;
	vec3 samplePos;
	while (sampleCol < 1.0 && dist < maxDist) {
		samplePos = dir * dist + origin;
		float mip = max(log2(diam * voxelgiResolution.x), 0);
		float mipSample = textureLod(voxels, samplePos * 0.5 + vec3(0.5), mip).r;
		sampleCol += (1 - sampleCol) * mipSample;
		dist += max(diam / 2, VOXEL_SIZE);
		diam = dist * aperture;
	}
	return sampleCol;
}

float traceShadow(sampler3D voxels, const vec3 origin, const vec3 dir) {
	return traceConeAO(voxels, origin, dir, 0.14 * voxelgiAperture, 2.5 * voxelgiRange);
}

float traceAO(const vec3 origin, const vec3 normal, sampler3D voxels) {
	const float angleMix = 0.5f;
	const float aperture = 0.55785173935;
	vec3 o1 = normalize(tangent(normal));
	vec3 o2 = normalize(cross(o1, normal));
	vec3 c1 = 0.5f * (o1 + o2);
	vec3 c2 = 0.5f * (o1 - o2);

	#ifdef HLSL
	const float factor = voxelgiOcc * 0.93;
	#else
	const float factor = voxelgiOcc * 0.90;
	#endif
	
	#ifdef _VoxelCones1
	return traceConeAO(voxels, origin, normal, aperture, MAX_DISTANCE) * factor;
	#endif

	#ifdef _VoxelCones3
	float col = traceConeAO(voxels, origin, normal, aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, o1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -c2, angleMix), aperture, MAX_DISTANCE);
	return (col / 3.0) * factor;
	#endif

	#ifdef _VoxelCones5
	float col = traceConeAO(voxels, origin, normal, aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, o1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, o2, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -c1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -c2, angleMix), aperture, MAX_DISTANCE);
	return (col / 5.0) * factor;
	#endif
	
	#ifdef _VoxelCones9
	float col = traceConeAO(voxels, origin, normal, aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, o1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, o2, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -c1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -c2, angleMix), aperture, MAX_DISTANCE);

	col += traceConeAO(voxels, origin, mix(normal, -o1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, -o2, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, c1, angleMix), aperture, MAX_DISTANCE);
	col += traceConeAO(voxels, origin, mix(normal, c2, angleMix), aperture, MAX_DISTANCE);
	return (col / 9.0) * factor;
	#endif

	return 0.0;
}

#endif