HLSL Sequence Generators

generators.inc

float2 hammersley(uint index) {
    // Compute Hammersley sequence
    // TODO: these should come from uniforms
    // TODO: we should do this with logical bit operations
    const uint numSamples = uint(IBL_INTEGRATION_IMPORTANCE_SAMPLING_COUNT);
    const uint numSampleBits = uint(log2(float(numSamples)));
    const float invNumSamples = 1.0 / float(numSamples);
    uint i = uint(index);
    uint t = i;
    uint bits = 0u;
    for (uint j = 0u; j < numSampleBits; j++) {
        bits = bits * 2u + (t - (2u * (t / 2u)));
        t /= 2u;
    }
    return float2(float(i), float(bits)) * invNumSamples;
}