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#define M_PI 3.14159265359
layout(push_constant, binding = 1, std430) uniform Params {
uint face_id;
uint sample_count;
float roughness;
bool use_direct_write;
float face_size;
}
params;
vec3 texelCoordToVec(vec2 uv, uint faceID) {
mat3 faceUvVectors[6];
// -x
faceUvVectors[1][0] = vec3(0.0, 0.0, 1.0); // u -> +z
faceUvVectors[1][1] = vec3(0.0, -1.0, 0.0); // v -> -y
faceUvVectors[1][2] = vec3(-1.0, 0.0, 0.0); // -x face
// +x
faceUvVectors[0][0] = vec3(0.0, 0.0, -1.0); // u -> -z
faceUvVectors[0][1] = vec3(0.0, -1.0, 0.0); // v -> -y
faceUvVectors[0][2] = vec3(1.0, 0.0, 0.0); // +x face
// -y
faceUvVectors[3][0] = vec3(1.0, 0.0, 0.0); // u -> +x
faceUvVectors[3][1] = vec3(0.0, 0.0, -1.0); // v -> -z
faceUvVectors[3][2] = vec3(0.0, -1.0, 0.0); // -y face
// +y
faceUvVectors[2][0] = vec3(1.0, 0.0, 0.0); // u -> +x
faceUvVectors[2][1] = vec3(0.0, 0.0, 1.0); // v -> +z
faceUvVectors[2][2] = vec3(0.0, 1.0, 0.0); // +y face
// -z
faceUvVectors[5][0] = vec3(-1.0, 0.0, 0.0); // u -> -x
faceUvVectors[5][1] = vec3(0.0, -1.0, 0.0); // v -> -y
faceUvVectors[5][2] = vec3(0.0, 0.0, -1.0); // -z face
// +z
faceUvVectors[4][0] = vec3(1.0, 0.0, 0.0); // u -> +x
faceUvVectors[4][1] = vec3(0.0, -1.0, 0.0); // v -> -y
faceUvVectors[4][2] = vec3(0.0, 0.0, 1.0); // +z face
// out = u * s_faceUv[0] + v * s_faceUv[1] + s_faceUv[2].
vec3 result = (faceUvVectors[faceID][0] * uv.x) + (faceUvVectors[faceID][1] * uv.y) + faceUvVectors[faceID][2];
return normalize(result);
}
vec3 ImportanceSampleGGX(vec2 Xi, float Roughness, vec3 N) {
float a = Roughness * Roughness; // DISNEY'S ROUGHNESS [see Burley'12 siggraph]
// Compute distribution direction
float Phi = 2.0 * M_PI * Xi.x;
float CosTheta = sqrt((1.0 - Xi.y) / (1.0 + (a * a - 1.0) * Xi.y));
float SinTheta = sqrt(1.0 - CosTheta * CosTheta);
// Convert to spherical direction
vec3 H;
H.x = SinTheta * cos(Phi);
H.y = SinTheta * sin(Phi);
H.z = CosTheta;
vec3 UpVector = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
vec3 TangentX = normalize(cross(UpVector, N));
vec3 TangentY = cross(N, TangentX);
// Tangent to world space
return TangentX * H.x + TangentY * H.y + N * H.z;
}
// https://graphicrants.blogspot.com.au/2013/08/specular-brdf-reference.html
float GGX(float NdotV, float a) {
float k = a / 2.0;
return NdotV / (NdotV * (1.0 - k) + k);
}
// https://graphicrants.blogspot.com.au/2013/08/specular-brdf-reference.html
float G_Smith(float a, float nDotV, float nDotL) {
return GGX(nDotL, a * a) * GGX(nDotV, a * a);
}
float radicalInverse_VdC(uint bits) {
bits = (bits << 16u) | (bits >> 16u);
bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
return float(bits) * 2.3283064365386963e-10; // / 0x100000000
}
vec2 Hammersley(uint i, uint N) {
return vec2(float(i) / float(N), radicalInverse_VdC(i));
}
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