Function ProjectCubemapToSH

SampleFramework11/v1.01/Graphics/SH.cpp:118–155

SH9Color ProjectCubemapToSH(ID3D11Device* device, ID3D11ShaderResourceView* cubeMap)
{
    TextureData<Float4> textureData;
    GetTextureData(device, cubeMap, textureData);
    Assert_(textureData.NumSlices == 6);
    const uint32 width = textureData.Width;
    const uint32 height = textureData.Height;

    SH9Color result;
    float weightSum = 0.0f;
    for(uint32 face = 0; face < 6; ++face)
    {
        for(uint32 y = 0; y < height; ++y)
        {
            for(uint32 x = 0; x < width; ++x)
            {
                const uint32 idx = face * (width * height) + y * (width) + x;
                Float3 sample = textureData.Texels[idx].To3D();

                float u = (x + 0.5f) / width;
                float v = (y + 0.5f) / height;

                // Account for cubemap texel distribution
                u = u * 2.0f - 1.0f;
                v = v * 2.0f - 1.0f;
                const float temp = 1.0f + u * u + v * v;
                const float weight = 4.0f / (sqrt(temp) * temp);

                Float3 dir = MapXYSToDirection(x, y, face, width, height);
                result += ProjectOntoSH9Color(dir, sample) * weight;
                weightSum += weight;
            }
        }
    }

    result *= (4.0f * 3.14159f) / weightSum;
    return result;
}

}