2D Gaussian Blur for Houdini using VEX

gaussianblur2d.c

float sigma = chf("sigma");
int res = chi("res");
int resx = chi("resx");
int resy = chi("resy");
int resn = floor(res / 2.0);
float weightTotal = 0;
float valTotal = 0;
for(int i=-resn; i<=resn; i++){
    for(int n=-resn; n<=resn; n++){
        float ix = @ptnum % resx + i;
        float iy = floor(@ptnum / float(resx)) + n;
        
        ix = min(max(0, ix), resx-1);
        iy = min(max(0, iy), resy-1);
                
        float nu = 1.0 / (2 * $PI * sigma * sigma);
        float weight = exp(-(i * i + n * n) / (2 * sigma * sigma)) * nu;
        weightTotal += weight;
        
        int ptnum = int(iy * resx + ix);
        float val = point(0, "val", ptnum);
        val *= weight;
        valTotal += val;
    }
}

valTotal /= weightTotal;

f@val = valTotal;