Mesh set question

[Carl Ollivier-Gooch]

Mark Shephard wrote:
> Is there documentation on the rules for mesh sets under mesh modification?
> 
> For example what happens in the following case:
> 
> 2-D mesh and I want to swap an edge between two mesh faces that are in 
> different mesh sets.
> 
> Which mesh set do the new faces go into, or do they not go into either 
> mesh set?

This raises several issues.

1.  Depending on what the mesh sets represent, you may or may not want 
to do the swap.  For instance, if the sets represent different 
materials, the swap is obviously a bad idea.  This implies that services 
that swap should allow apps to specify whether multi-set swaps are legal.

2.  We don't (as I recall) have a way of finding out which set an entity 
is in, other than checking it against every set, which implies that 
services that swap aren't going to be able to care about set membership 
efficiently.

And, in answer to the original question, I don't have any clue which set 
those new faces belong in, so I'd prefer not to put them in any set. 
That's true even if they're both in the same set:  it could be a set of 
faces that need to be swapped, and the new ones won't necessarily need 
to be anymore...

Oh, and while you're worrying about metadata under mesh modification, we 
also can't efficiently find out whether an entity is used as a tag on 
some other entity, so that we could at least delete that tag data when 
the entity is removed.

Anyone with brilliant ideas on how to fix any of this, please speak 
right up. :-)

Carl

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