I have a strange problem with a uv map that no amount of googling has been able to solve. Basically, a single vertex in a UV map has almost no effect on that map. I’ve already tried everything I can think of including
Seams / no seams
deleting uv map and re-creating
resetting uv map
unwrapping again
re-creating projection again
turning on/off uv sync
disabling / enabling sticky selection mode
ensuring scale of mesh is set to 1
ensuring there are no overlapping vertices / edges by using mesh cleanup (merge vertices) etc.
Here are some images that show the problem. The first image shows the UV map in its normal state. The second image shows a working vertex distorting the map properly when moved around. The third image shows the “broken” vertex that has a near zero effect on the map when moved.
I’m trying to figure out how to make that one broken vertex behave and have the proper effect on the map. I’ve also included a picture of the mesh in wireframe mode so you can see there are no hidden edges connecting the 2 vertices on either side of the broken one.
Oh I had no idea it worked that way. Thank you! Funny enough I had been editing this model because Unity complained about self-intersecting meshes and I had been going through all my models and triangulating all faces with more than 4 sides to get rid of the warnings.
I can see from the picture below that the UV map uses some hidden internal triangulation that is not visible until you distort the image in certain ways. I’d actually been wondering why certain distortions resulted in the uv map folding back on itself and others didn’t. This explains it perfectly. I suppose in this case, it’s better to split the face manually before uv mapping in a way that is compatible with how you intend to distort the uv map.
Do you know if it’s possible to display the uv map triangulation without splitting the face first, or it only shows up when you move the vertices like in the picture below?
Yes. There is always hidden triangulation step, because GPUs can only render triangles.
I don’t recommend distorting UVs on Ngons, because its not exacly predictable behavior of how it will be triangulated if You wont have triangulate step on it.
Anything except triangle does not garantee that You will get what You want. Even quad can be “wrong”:
Because same quad and ngon can be triangulated in multiple ways and different programs do have different triangulate algorithms to have exact matching results You should always export Your models triangulated to Your game engine (just add triangulate modifier at end of modifiers stack) and for baking to ensure it will be triangulated in same way as you see it in Blender.
