Function GenerateUniformSGs

BakingLab/SG.cpp:29–65

Generate uniform spherical gaussians on the sphere or hemisphere

// Generate uniform spherical gaussians on the sphere or hemisphere
static void GenerateUniformSGs(SG* sgs, uint64 numSGs)
{
    uint64 N = numSGs * 2;

    Assert_(numSGs <= uint64(AppSettings::MaxSGCount));

    Float3 means[AppSettings::MaxSGCount * 2];

    float inc = Pi * (3.0f - std::sqrt(5.0f));
    float off = 2.0f / N;
    for(uint64 k = 0; k < N; ++k)
    {
        float y = k * off - 1.0f + (off / 2.0f);
        float r = std::sqrt(1.0f - y * y);
        float phi = k * inc;
        means[k] = Float3(std::cos(phi) * r, std::sin(phi) * r, y);
    }

    uint64 currSG = 0;
    for(uint64 i = 0; i < N; ++i)
    {
        // For the sphere we always accept the sample point but for the hemisphere we only accept
        // sample points on the correct side of the hemisphere
        if(Float3::Dot(means[i].z, Float3(0.0f, 0.0f, 1.0f)) >= 0.0f)
        {
            SG sample;
            sample.Axis = Float3::Normalize(means[i]);
            sgs[currSG++] = sample;
        }
    }

    Float3 h = Float3::Normalize(sgs[1].Axis + sgs[0].Axis);
    float sharpness = (std::log(0.65f) * numSGs) / ((Float3::Dot(h, sgs[0].Axis) - 1.0f));

    for(uint32 i = 0; i < numSGs; ++i)
        sgs[i].Sharpness = sharpness;
}

void InitializeSGSolver(uint64 numSGs)
{