Why isn't it possible, to connect 2 identical uv-islands, turning them into single one.

Creepezel

This at least seems more time saving option for me. As for now, what I see in Blender at least, mirrored face works by laying 2 identical uv-islands on the same position, but that doesn't make them a single uv-island in practice. Why can't they become one (2 sides of the mesh, using the same single uv-island) ? Wouldn't it make editing uv easier, if, let's say, you were ordered to make some changes ? There wouldn't be a need to cut the mesh in half again just to apply changes, then pack uv-islands on the texture space before applying mirror modifier.

So, is there some reason, why mirrored island must be 2 separated ones ?

DavidCruz

Normals (comes to mind) i.e. light shading.
^ Answer.

Otherwise, if its diffuse texture only (hand painted and everything is a mirror you are right and can 'weld - in max anyway the verts down and move 1 (dot) vert to fix and or adjust the u.v.'s as you explain it., IF they are 1:1

Unless they have objects or things in the way where being mirrored would cause an oddity, say a scar or tattoo or some design.)

If i am miss understanding, i must've read the post wrong, hopefully this is correct if not i am sure someone will come around to correct it.

monster

It is possible in Max, like David says, but only if you turn off certain hidden options.

Really though, if your still editing the geometry or UVs just delete half of your model and reapply the symmetry when you are done.