void psetr(int d, int m, int z, int v)
This function sets the value of one channel for a pixel in the output buffer, using polar coordinates (rather than cartesian) to address the pixel; the polar coordinates are relative to the image center. The channel to be set is given by 'z' (0 = red, 1 = green, 2 = blue, and 3 = alpha). NOTE: There is no guarantee that this function is able to completely populate the plane - some pixels in the output buffer may be unreachable because of rounding errors.
%ffp ForEveryTile: { int d, m; for (d=0; d<1024; ++d) { for (m=0; m<256; m+=3) { for (z=0; z<Z; ++z) { psetr(d, m, z, 256); } } } return true; }
Everyone can add his comments about his experiences with this function here. Tips for using it are welcome, too.