Hi PaQ,

Yeah that ability of Maya to transform subd to NURBS does not seem to be very frequently mentioned or used for some reason. But it could definitely be a useful transfer method.


> Here's a other try using maya, still thinking it might be a cool way of
> working ... however there as some areas that are quite
> complex (red lines) and need probably to be rebuild/simplify too.

That kind of smaller patch refinement will generally happen in areas where you have a vertex with a valence of other than 4, meaning more than 4 edges radiating out from it.

Like in this case you seem to have a kind of edge loop that terminates here:



So that created a vertex there that has a valence of 3, and the one right above it has a valence of 5 with 5 edges coming out of it - if you can avoid those where possible then it will probably eliminate that kind of patch refinement.

Like in your case here if you continue that edge loop to the end instead of terminating it, that will probably get fixed up.


There is a common relationship between some of the mechanics of how NURBS surfaces work and how subd surfaces work.

The way that Catmull-Clark subd works, it is actually completely equivalent to a NURBS surface in areas of the subd that have quad polygons with all vertices of valence 4.

Those areas of the subd surface have an exact and natural translation to a NURBS surface.

Areas where that is not the case like at your valence 5 spot, do not have a natural equivalence to NURBS so those areas get processed with a kind of fitting or refinement type scheme to get some NURBS surfaces in there that are close enough to the subd surface. But the refinement will generate additional surfaces, that is what you are seeing there.

- Michael