Hi all, I need an algorithm that fills a 3d lattice from any point, always expanding (no return allowed as in ref. http://msl.cs.illinois.edu/~lavalle/papers/KufLav09.pdf). The cells must be visited just once. My efforts are contained in the attached file. It works ***almost*** correct. Some gaps remain, though. No matter my attempts I could not fix the code. Could you help me, fixing the code or cite an alternate reference? The executable (Tree.exe) can use the mouse for orbital rotations and the following keys and conventions: 1 shows root 2 shows x axis 3 shows y axis 4 shows z axis 5 shows xy plane 6 shows yz plane 7 shows zx plane 8 shows octant spirals q selects the first octant only a shows positive axes pgup increases dimension pgdwn decreases dimension The not visited positions are shown as a white dot. The relevant algorithm is contained in the functions expandTree() and isAllowed() in file 'forum.c'. Thanks for any help.