Named Selections no longer working after mesh uv unwrap

Hello,

This is a bug or at least a limitation.
For example, look at this very serious task of UV mapping toilet seat :wink:

Named selection degenerates after modifying the mesh - UV Texture unwrapping unwelds some mesh edges and because of that Named Selection made before unwrapping no longer works.

kibel.3dm (3.0 MB)

Before unwrapping


After unwrapping

I can see how welding/unwelding could trip up a saved edge selection. But ideally any saved faces/polygons selections should always try to survive any welding, unwrapping, even exploding, correct?

G

I’m not a mesh expert, but from a user perspective, yeah it totally should survive, especially in cases where not a single polygon is moved or added.

And sometimes it survives e.g. welding edges which is really great but it needs to be this way every time.

Hello - unwrapping, if you specify seams, changes the number of vertices and ‘edges’ (which do not really exist as they do on breps) so any indexing to the previous mesh is completely useless.

-Pascal

Hi Pascal, yes, that’s the way its done today, because Rhino’s logic is very rudimentary. For example, even if specifying seams changes the number of edges, because they get duplicated, those edges are sharing same exact positions, and they have been doubled up by a command (a trackable event). So I think there’s room here for Rhino to keep track of this and know that an old loop is now two coincident loops.

Modo for example can even keep UV unwrapping information, even if you add/removes polys from a model. How do they do that? they designed their system to be paying attention to neighboring geometry and to what commands are the ones changing what.

It can be done, and like all good work, it’s just more work. I think this, like any other form of non-destructive editing is also important work.

G

Right… I did not mean to imply that it is impossible or anything; I should have added “the way Rhino meshes currently work”.

-Pascal

1 Like