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uniform samplerCube probeHdr;
uniform float roughnessSquared;
uniform float lodFactor;
uniform float lodMax;
in vec3 worldPosition;
out vec4 FragColor;
void main() {
vec3 N, T, B, V;
vec3 R = normalize(worldPosition);
/* 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(out_radiance / weight, 1.0);
}
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