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uniform samplerCube probeHdr;
uniform float roughnessSquared;
uniform float texelSize;
uniform float lodFactor;
uniform float lodMax;
uniform float paddingSize;
uniform float intensityFac;
in vec3 worldPosition;
out vec4 FragColor;
vec3 octahedral_to_cubemap_proj(vec2 co)
{
co = co * 2.0 - 1.0;
vec2 abs_co = abs(co);
vec3 v = vec3(co, 1.0 - (abs_co.x + abs_co.y));
if ( abs_co.x + abs_co.y > 1.0 ) {
v.xy = (abs(co.yx) - 1.0) * -sign(co.xy);
}
return v;
}
void main() {
vec2 uvs = gl_FragCoord.xy * texelSize;
/* Add a N pixel border to ensure filtering is correct
* for N mipmap levels. */
uvs += uvs * texelSize * paddingSize * 2.0;
uvs -= texelSize * paddingSize;
/* edge mirroring : only mirror if directly adjacent
* (not diagonally adjacent) */
vec2 m = abs(uvs - 0.5) + 0.5;
vec2 f = floor(m);
if (f.x - f.y != 0.0) {
uvs = 1.0 - uvs;
}
/* clamp to [0-1] */
uvs = fract(uvs);
/* get cubemap vector */
vec3 cubevec = octahedral_to_cubemap_proj(uvs);
vec3 N, T, B, V;
vec3 R = normalize(cubevec);
/* Isotropic assumption */
N = V = R;
make_orthonormal_basis(N, T, B); /* Generate tangent space */
/* Noise to dither the samples */
/* Note : ghosting is better looking than noise. */
// setup_noise();
/* Integrating Envmap */
float weight = 0.0;
vec3 out_radiance = vec3(0.0);
for (float i = 0; i < sampleCount; i++) {
vec3 H = sample_ggx(i, roughnessSquared, N, T, B); /* Microfacet normal */
vec3 L = -reflect(V, H);
float NL = dot(N, L);
if (NL > 0.0) {
float NH = max(1e-8, dot(N, H)); /* cosTheta */
/* Coarse Approximation of the mapping distortion
* Unit Sphere -> Cubemap Face */
const float dist = 4.0 * M_PI / 6.0;
float pdf = pdf_ggx_reflect(NH, roughnessSquared);
/* http://http.developer.nvidia.com/GPUGems3/gpugems3_ch20.html : Equation 13 */
float lod = clamp(lodFactor - 0.5 * log2(pdf * dist), 0.0, lodMax) ;
out_radiance += textureLod(probeHdr, L, lod).rgb * NL;
weight += NL;
}
}
FragColor = vec4(intensityFac * out_radiance / weight, 1.0);
}
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