+++ /dev/null
-#version 330
-
-in vec2 texCoords;
-out vec4 fragColor;
-
-const float PI = 3.14159265359;
-
-//TODO: Put this in a separate shader program
-float radicalInverse(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;
-}
-
-vec2 hammersley(uint i, uint N) {
- return vec2(float(i) / float(N), radicalInverse(i));
-}
-
-float geometrySchlickGGX(float NdotV, float roughness) {
- float a = roughness * roughness;
- float k = (a * a) / 2.f;
-
- return NdotV / (NdotV * (1.f - k) + k);
-}
-
-float geometrySmith(vec3 N, vec3 V, vec3 L, float roughness) {
- float ggx1 = geometrySchlickGGX(max(dot(N, L), 0.f), roughness);
- float ggx2 = geometrySchlickGGX(max(dot(N, V), 0.f), roughness);
- return ggx1 * ggx2;
-}
-
-vec3 importanceSampleGGX(vec2 Xi, vec3 N, float roughness) {
- float a = roughness * roughness;
-
- float phi = 2.f * PI * Xi.x;
- float cosTheta = sqrt((1.f - Xi.y) / (1.f + (a * a - 1.f) * Xi.y));
- float sinTheta = sqrt(1.f - cosTheta * cosTheta);
-
- // spherical -> cartesian
- vec3 H = vec3(cos(phi) * sinTheta, sin(phi) * sinTheta, cosTheta);
-
- vec3 up = abs(N.z) < 0.999 ? vec3(0, 0, 1) : vec3(1, 0, 0);
- vec3 tangent = normalize(cross(up, N));
- vec3 bitangent = cross(N, tangent);
-
- vec3 sampleVec = tangent * H.x + bitangent * H.y + N * H.z;
- return normalize(sampleVec);
-}
-
-vec2 integrateBRDF(float NdotV, float roughness) {
- vec3 V = vec3(sqrt(1.f - NdotV * NdotV), 0.f, NdotV);
-
- float A = 0, B = 0;
-
- vec3 N = vec3(0, 0, 1);
-
- const uint sampleCount = 1024u;
- for (uint i = 0u; i < sampleCount; i++) {
- vec2 Xi = hammersley(i, sampleCount);
- vec3 H = importanceSampleGGX(Xi, N, roughness);
- vec3 L = normalize(2.f * dot(V, H) * H - V);
-
- float NdotL = max(L.z, 0.f);
- float NdotH = max(H.z, 0.f);
- float VdotH = max(dot(V, H), 0.f);
-
- if (NdotL > 0) {
- float G = geometrySmith(N, V, L, roughness);
- float Gvis = (G * VdotH) / (NdotH * NdotV);
- float Fc = pow(1.f - VdotH, 5.f);
-
- A += (1.f - Fc) * Gvis;
- B += Fc * Gvis;
- }
- }
-
- A /= float(sampleCount);
- B /= float(sampleCount);
-
- return vec2(A, B);
-}
-
-void main() {
- fragColor = vec4(integrateBRDF(texCoords.x, texCoords.y), 0, 0);
-}
-
-