UV mapping not working right

Hello everyone, this is my first post on the BlenderArtists forum, I am not sure where exactly I should have posted this so I am sorry if it’s in the wrong place…

I am having a problem with the UV mapping of my human model. I have created it using the mirror modifier so I know that it is 100% symmetrical, but when I try to create a UV map of the face area, the result shows one side of the mouth wider than the other, as if the model is sneering at me! I have checked, double checked and triple checked the topology of the mouth area and applied the mirror modifier several times to ensure that the model is definitely 100% symmetrical, but the end result is always the same, with one side of the mouth larger than the other. How can I fix this???

Have you checked your normals? Be certain they are all facing out. The UV unwrapper might be unwrapping half of your face inside out.

Yes I’ve triple checked everything in sight, I was working on this issue for an entire day and for the life of me I don’t understand it. There is CLEARLY only ONE vertex on the mesh but on the UV unwrap it shows TWO vertices with a gap inside the mesh - I checked normals, I checked duplicates, I made UV unwraps every time I made a modification - but I was still getting the gap - eventually I decided to delete the side of the mouth and rebuild it, and I still got the exact same problem! But strangely, I closed Blender and then opened it again, reloaded the file… and the UV mesh did not show a gap after that. However, it still had one side of the mouth much larger than the other, even after rebuilding one side of the mesh using the mirror modifier!

I eventually managed to solve that too, by applying the mirror modifier to create both sides of the mesh and then rebuilding both sides of the mouth by hand, making sure that I was mirroring what I did on both sides manually, which was obviously a pain to do without using the modifier again. So, now my UV unwrap is looking great and both the split-in-the-cheek error and the one-side-of-the-mouth-larger-than-the-other error are both gone - but I am now dying to know exactly what might have caused this, because if it’s happening to me now, its going to happen again in the future :frowning:

I spoke to a friend of mine who is much more experienced at Blender than I am, and he said that he has also had the exact same problems before, and he also had to solve it the same way I did. We are both wondering why this happens. If anyone can enlighten us, please let us know :slight_smile:

I hate to say it, but Blender is not perfect. I encounter weird errors all the time. I am glad you solved your problem, but yes, Blender has it’s issues. I’m using 2.49b, but perhaps when a finished version of 2.5 comes out some of these weird issues will be solved. Frustrating day I imagine! Welcome to the forum.

I made a little blend file, that shows how it might happen.
By simply applying the mirror modifier once and
turning on the “apply mirror while editing”,
it looks like UV unwraps a completely symmetric mesh wrong.
In fact it is unwrapping a asymmetric mesh perfectly right.

messedmirror.blend (136 KB)

Although some mirrored vertexes happen to get mapped to the same coordinates the “remove double” will not see.

Well in my blender 2.49b the UV unwraps only the “real” part of the mesh.
Only after applying the mirror modifier the other half is unwrapped too.
So when you see both halves asymmetrically unwrapped, you can bet there is geometry you do not want that way.

and applied the mirror modifier several times
Apply the mirror modifier and remove double in the above file will end up in a complete disaster.
Try it :slight_smile:
And far away from generating something symmetric.
Don’t trust in “apply mirror while editing” to fix it for you.
Once you have garbage on the mirror side it will stay there until you manually remove it.

The cure:

  1. Remove mirror from mesh.
  2. In edit mode make sure there is really only one half.
  3. Add mirror
  4. Edit mesh
  5. In edit mode make sure there is really only one half.
  6. Apply mirror
  7. Mark seams
  8. Unwrap.

need to do symmetric editing start over at 2.

Ah thank you :slight_smile: I was hoping it wasn’t some major error within Blender :slight_smile: I actually fixed the problem eventually but I wasn’t sure how. At least now I can follow your instructions and hopefully fix or avoid this situation in the future :slight_smile: