Quote - Ahh - thanks for the info.  I am a little confused about your explaination though -  maybe it's a matter of semantics / terminology, but...

Quote - ...They match mesh topology, not positions or orderings...

From my understanding, 'mesh topology' is basically defined by the layout of the polygons, which in turn are defined by the 'positions' of the vertices that make up those polygons.  I don't know how you could be comparing mesh topologies without (ultimately) comparing vertex positions (?).

When I say topology, I mean what you get when you look at a basic OBJ file without texture coordinates or normals and ignore everything but the 'f' lines. Basically, that tells you that have a certain number of vertices, numbered from 1 to, say, 14512, and that certain cyclic sequences of these form polygons. If you change all the numbers consistently - say, you add 1000 to each - you still get the same topology.

So, imagine you had the 'f' lines for two meshes which you suspect to be the same, but mesh B so radically morphed away from the shape that mesh A had that comparing vertex positions wouldn't help, and also the vertex numbering completely screwed up by the program you did the morphing in. Then, if you also had a lot - and I mean a lot - of computing time, you could still figure out which vertices in A correspond to which vertices in B by simply going through all the possible ways of renumbering the vertices in B and testing for each if the result coincides with A.

Of course, it would be pretty silly to go through all possible numberings of the vertices. If your meshes are connected, and you have found a small patch - a single polygon would be sufficient - of mesh A that corresponds to a similar patch in mesh B, all the rest will be completely determined and you just need to verify that your partial match indeed extends to a complete match. Furthermore, poles in one mesh should corresponds to poles in the other one, so you can save a lot more work by picking a pole in mesh A and matching it to poles in mesh B.

I hope that clarifies some things. :-)

[/nerd]

 

-- I'm not mad at you, just Westphalian.