Parts of mesh unwrapping inside-out

Hi everyone

I’m making an animation of a planetary gear system, but I’ve run into a problem with the way the ring gear is unwrapping. The parts with the teeth unwrap inside-out, with the teeth facing outward rather than inward.

The first time I unwrapped it, there was an alert in the header that said something like Object has a negative scale, so… (something about how it was going to unwrap, but it disappeared before I could read the whole thing). But I had applied scale and rotation before unwrapping, and I verified that the xyz scale in Properties was 1,1,1.

If I unwrap it using “Smart UV Project” the teeth point the right way, but it puts seams where I don’t want them and I can’t seem to prevent that by adding new seams or changing the angle setting in the Smart UV Unwrap window.

I have searched this problem and tried all the suggestions about recalculating normals. When I view the normals they all look as though they are pointing the right direction.

It’s not the end of the world, I can texture this to my satisfaction despite the issue, but it’s a puzzle I’d really like to solve if for no other reason than to try to maintain my sanity. :spin:

I have attached a blend file with the problem model.

Thanks for any help you can provide!


ring-gear-unwrap-problem.blend (670 KB)