Issue with UVs?

Helixx

Hey guys, kinda sad that my first post had to be a question but I've run into a little snag with my model. For a little background, I'm a 3d max/Zbrush user, using max to model low poly and using zbrush to detail. Now onto my problem.

The first image is a render with basic 3 point lighting just to get some detail from the normal map while I work on the model. It looks to me as if there are 8 polygons that have gone wonky yet I can't seem to figure out why.



The second image is a render of the model where I've used the uvw template max renders out on a screen layer overtop of the actual texture and I used red dots at the top left corners of the polys to make sure they didn't get flipped or anything.



After looking at the model, the uvs, the normal map, it doesn't seem like anything should be wrong.

The last image is a screenshot of the model without the render showing no issue at all.



If anyone has suggestions or ideas as to what might be causing the anomaly please let me know. Thanks in advance to anyone who replies.

Eric Chadwick

Does that section have a different smoothing group than the rest? Is your UV layout seamless in that area? Are all the vertices in that area welded? Can you show the normal map for that area? Could be any or all of these things.

Helixx

Thanks for the reply. I rechecked the smoothing groups to make sure it wasn't different ones. It's all one smoothing group and there are no unwelded vertices. There is a seam but it runs down the middle of the back only which I'd think would give me an issue all the way up the back if it did have an issue.

Here's a shot of my normal map pieces with the polys in question circled. You'll notice that there's no anomalies that would cause what I'm seeing.





Let me know what you think.

Ott

Turn the normal map off and re-render - what do you get?

This will help to determine if it is a normal map issue or a geometry issue.

Check your elements, flipped normals on export/import, and make sure that the polygons are on the proper material ID. Those are just a couple off the top of my head.

Maybe making it all one smoothing group is causing the problem rather than helping it...if you look closely at the small of his back in your non-wireframe shot it looks like the same thing is happening down there.

Eric Chadwick

You can also use a STL Check modifier to find mistakes, like doubled faces, open edges, etc.

Helixx

Well I solved the problem but it was really something I didn't think would matter. It appears it was calculating light wrong because my unwrap was collapsed into the stack. Once I applied another UVWunwrap modifier and re-welded all the verts it looked fine. Thanks for all your help guys, sorry for the wild goose chase. I'll post the final render once I get it done so you guys can have a looksee

Eric Chadwick

Unwelded UV verts, or unwelded mesh verts?

Helixx

It was caused by unwelded verts in the unwrap.

Eric Chadwick

Cool, thanks, just in case I run into the same thing.