btw, the thing with the twisting suzzane is neat... you could use that for an animation where the creature is curling and twisting from vines or goo into being - the final boss! lol ;) Thanks!

Hi artislight, thanks for the comments. If I understand correctly, El Topo tracks the surface with a tidy triangular mesh consisting of more and less equal-sized triangles. The triangles that have become larger than a threshold are automatically splitted, whereas those triangles that have shrinked too much are merged. I thought surface tracking would be an ideal modeling tool to be used with Freestyle, since El Topo maintains a clean topology of edges, while in Freestyle we need edges where we want to draw strokes. An open issue that I encountered was that Catmull-Clark subsurf modifier appeared not to work well with a triangular mesh; to get a smooth surface to be tracked by El Topo, a finer triangular mesh (i.e. a smaller threshold) would be needed, which will increase the computation time. That said, surface tracking is certainly a cool tool. I would like to find out an effective way of using it with Freestyle.

great!
is there some info about El Topo? i try googling, but i haven't found anything important. Thanks a lot!

Hi Martin,
El Topo is available in the following place:
cs.ubc.ca/labs/imager/tr/2009/eltopo/eltopo.html