3 in vec3 localPos, normal;
6 uniform samplerCube environmentMap;
7 uniform float roughness;
9 const float PI = 3.14159265359;
11 //TODO: Put this in a separate shader program
12 float radicalInverse(uint bits) {
13 bits = (bits << 16u) | (bits >> 16u);
14 bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
15 bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
16 bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
17 bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
18 return float(bits) * 2.3283064365386963e-10;
21 vec2 hammersley(uint i, uint N) {
22 return vec2(float(i) / float(N), radicalInverse(i));
25 vec3 importanceSampleGGX(vec2 Xi, vec3 N, float roughness) {
26 float a = roughness * roughness;
28 float phi = 2.f * PI * Xi.x;
29 float cosTheta = sqrt((1.f - Xi.y) / (1.f + (a * a - 1.f) * Xi.y));
30 float sinTheta = sqrt(1.f - cosTheta * cosTheta);
32 // spherical -> cartesian
33 vec3 H = vec3(cos(phi) * sinTheta, sin(phi) * sinTheta, cosTheta);
35 vec3 up = abs(N.z) < 0.999 ? vec3(0, 0, 1) : vec3(1, 0, 0);
36 vec3 tangent = normalize(cross(up, N));
37 vec3 bitangent = cross(N, tangent);
39 vec3 sampleVec = tangent * H.x + bitangent * H.y + N * H.z;
40 return normalize(sampleVec);
44 vec3 N = normalize(localPos);
46 // approximate view direction - no grazing specular reflections
50 const uint sampleCount = 1024u;
51 float totalWeight = 0;
52 vec3 prefilteredColor = vec3(0);
53 for (uint i = 0u; i < sampleCount; i++) {
54 vec2 Xi = hammersley(i, sampleCount);
55 vec3 H = importanceSampleGGX(Xi, N, roughness);
56 vec3 L = normalize(2.f * dot(V, H) * H - V);
58 float NdotL = max(dot(N, L), 0.f);
60 prefilteredColor += texture(environmentMap, L).rgb * NdotL;
65 prefilteredColor = prefilteredColor / totalWeight;
66 fragColor = vec4(prefilteredColor, 1.f);