Subpixel Reconstruction Antialiasing

@InProceedings{CML11,
    author       = "Chajdas, Matth{\"a}us G. and Mc{G}uire, Morgan and Luebke, David",
    title        = "Subpixel Reconstruction Antialiasing",
    booktitle    = "Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games",
    year         = "2011",
    publisher    = "ACM Press"
}

float3 normal(int x, int y)
{
    return normalBuffer.Get(x, y) * 2.0 -
        make_float3(1, 1, 1);
}

float depth(int x, int y)
{
    return depthBuffer.Get(x, y);
}

float bilateral(float3 centerN, float centerZ,
                float3 tapN, float tapZ)
{
    return exp(-scale * max((1.0 - dot(centerN, tapN)),
        depthScale * abs(centerZ - tapZ)));
}

// Iterate the "center" (cx, cy) of the filter
// over the samples in the pixel at (x, y)
float weights[9] = {0};
for (int cy = y; cy < (y + 2); ++cy) {
    for (int cx = x; cx < (x + 2); ++cx) {
        float3 N = normal(cx, cy);
        float Z = depth(cx, cy);
        float tmpWeights[9] = {0};
        float sum = 0.0f;

        // Iterate over the neighboring samples
        for (int j = 0; j < 3; ++j) {
            for (int i = 0; i < 3; ++i) {
                // If inside filter support
                if ((abs(i - 1 - cx) <= 1) && (abs(j - 1 - cy) <= 1)) {
                    int tapX = x + i - 1;
                    int tapY = y + j - 1;
                    // Compute the filter weight
                    float w = bilateral (N, Z,
                        normal(tapX, tapY), depth(tapX, tapY));
                    tmpWeights[i + j * 3] = w;
                    sum += w;
                }
            }
        }

        for (int t = 0; t < 9; ++t) {
            weights[t] += tmpWeights[t] / sum;
        }
    }
}

// Apply the filter
float3 result = make_float3 (0, 0, 0);
for (int j = 0; j < 3; ++j) {
    for (int i = 0; i < 3; ++i) {
        result += weights[i + j * 3] * 0.25 *
        colorBuffer.Get(x + i - 1, y + j - 1);
    }
}