Matt,

Maybe I missed the multiplication by two for the two possible incrementations, so maybe it should be:

s = (ny*nx + nx*nz + nx*nz - 2) * 18

The issue is a typo, which is not surprising with those crazy numbers I got. Above is wrong, below is correct and is working in my tests. s = (ny*nx + nx*nz + ny*nz - 2) * 18   Stephen Skory stephenskory@yahoo.com http://stephenskory.com/ 510.621.3687 (google voice)