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uniform samplerCube probeHdr;
uniform int probeSize;
uniform float lodBias;
in vec3 worldPosition;
out vec4 FragColor;
#define M_4PI 12.5663706143591729
const mat3 CUBE_ROTATIONS[6] = mat3[](
mat3(vec3( 0.0, 0.0, -1.0),
vec3( 0.0, -1.0, 0.0),
vec3(-1.0, 0.0, 0.0)),
mat3(vec3( 0.0, 0.0, 1.0),
vec3( 0.0, -1.0, 0.0),
vec3( 1.0, 0.0, 0.0)),
mat3(vec3( 1.0, 0.0, 0.0),
vec3( 0.0, 0.0, 1.0),
vec3( 0.0, -1.0, 0.0)),
mat3(vec3( 1.0, 0.0, 0.0),
vec3( 0.0, 0.0, -1.0),
vec3( 0.0, 1.0, 0.0)),
mat3(vec3( 1.0, 0.0, 0.0),
vec3( 0.0, -1.0, 0.0),
vec3( 0.0, 0.0, -1.0)),
mat3(vec3(-1.0, 0.0, 0.0),
vec3( 0.0, -1.0, 0.0),
vec3( 0.0, 0.0, 1.0)));
vec3 get_cubemap_vector(vec2 co, int face)
{
return normalize(CUBE_ROTATIONS[face] * vec3(co * 2.0 - 1.0, 1.0));
}
float area_element(float x, float y)
{
return atan(x * y, sqrt(x * x + y * y + 1));
}
float texel_solid_angle(vec2 co, float halfpix)
{
vec2 v1 = (co - vec2(halfpix)) * 2.0 - 1.0;
vec2 v2 = (co + vec2(halfpix)) * 2.0 - 1.0;
return area_element(v1.x, v1.y) - area_element(v1.x, v2.y) - area_element(v2.x, v1.y) + area_element(v2.x, v2.y);
}
void main()
{
float pixstep = 1.0 / probeSize;
float halfpix = pixstep / 2.0;
float weight_accum = 0.0;
vec3 sh = vec3(0.0);
int shnbr = int(floor(gl_FragCoord.x));
for (int face = 0; face < 6; ++face) {
for (float x = halfpix; x < 1.0; x += pixstep) {
for (float y = halfpix; y < 1.0; y += pixstep) {
float shcoef;
vec2 facecoord = vec2(x,y);
vec3 cubevec = get_cubemap_vector(facecoord, face);
float weight = texel_solid_angle(facecoord, halfpix);
if (shnbr == 0) {
shcoef = 0.282095;
}
else if (shnbr == 1) {
shcoef = -0.488603 * cubevec.z * 2.0 / 3.0;
}
else if (shnbr == 2) {
shcoef = 0.488603 * cubevec.y * 2.0 / 3.0;
}
else if (shnbr == 3) {
shcoef = -0.488603 * cubevec.x * 2.0 / 3.0;
}
else if (shnbr == 4) {
shcoef = 1.092548 * cubevec.x * cubevec.z * 1.0 / 4.0;
}
else if (shnbr == 5) {
shcoef = -1.092548 * cubevec.z * cubevec.y * 1.0 / 4.0;
}
else if (shnbr == 6) {
shcoef = 0.315392 * (3.0 * cubevec.y * cubevec.y - 1.0) * 1.0 / 4.0;
}
else if (shnbr == 7) {
shcoef = 1.092548 * cubevec.x * cubevec.y * 1.0 / 4.0;
}
else { /* (shnbr == 8) */
shcoef = 0.546274 * (cubevec.x * cubevec.x - cubevec.z * cubevec.z) * 1.0 / 4.0;
}
vec4 sample = textureLod(probeHdr, cubevec, lodBias);
sh += sample.rgb * shcoef * weight;
weight_accum += weight;
}
}
}
sh *= M_4PI / weight_accum;
FragColor = vec4(sh, 1.0);
}
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