So at this stage we could import models from Maya with differences creases and it could be read in Rhino or I have to crease all the edges ?
I’m not optimistic.
This is a long answer, but it has enough information to pass onto Maya tech support to help you find an answer.
There are basically 3 types of edges in a Catmull-Clark SubD in a modern 3d modeling app.
Smooth - classic Catmull-Clark
Crease - (sharp crease with tangent discontinuity)
Sharp - (a blend between smooth and crease)
Some apps use the term “soft crease” for sharp edges.
Smooth edges are subdivided according to the original Catmull-Clark rules described in “Recursively generated B-spline surfaces on arbitrary topological meshes” by Catmull and Clark.
Crease edges are subdivided using the subdivision rules described in “Piecewise Smooth Subdivision Surfaces with Normal Control” by Biermann, Levin, and Zorin.
Sharp edges typically combine crease and smooth rules. For constant sharpness, many apps, including Rhino 8, use the method described in “Subdivision Surfaces in Character Animation” by DeRose, Kass, Troung. Variable sharpness edges use a variety of obvious extensions.
Rhino’s subdivision rules are described in Rhino SubD Rules
I will speculate that Maya and Rhino have very similar subdivision rules in their native code and any differences will be so slight as to not matter.
The issue with exchanging SubDs between two apps, say Maya and Rhino, is to find a file format that
- both apps read and write
- includes crease and sharp information.
If there is a Maya extension reads and writes .3dm files and that extension reads and writes Rhino 7 file format, then smooth and crease information can be exchanged. If that extension reads and writes Rhino 8 file format, then it can be enhanced so that smooth. crease and sharp information can be exchanged. We at McNeel would be delighted to help a 3rd party developer with this task.
If there is a 3rd party file format, like OBJ, USD, or 3DM, that Maya reads and writes and which accurately round-trips crease and sharp edges information in Maya, then it is very likely that Rhino 8 can support that extension to OBJ, USD, or 3DM.
If you can save a Maya model with crease and sharp edges in an OBJ, USD, or 3DM file, read that file back into Maya, and see that the crease and sharp edge information was correctly transmitted, then please post the file, a description of how it was created, and we will try very hard to read it into Rhino 8. If Maya cannot round trip crease and sharp edge information in a file it creates, then it is nearly certain Rhino can’t share crease and sharp edge information using that file format with Maya.
Cheers, Dale Lear
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