3DS Max - UV - inverted polygons?
polycounter lvl 4
Hey guys,
some faces get highlighted with the "select inverted polygon" option in my uv's but i dont know why. i checked them on following things:
1. with backface cull they are not inverted at the object
2. they got the same red full color like the others
3. i unify the normals with the "normal" modifier
4. i mirrored some of them in the uv to see if this works but still the same.
where is my problem and what can i do?
cheers
some faces get highlighted with the "select inverted polygon" option in my uv's but i dont know why. i checked them on following things:
1. with backface cull they are not inverted at the object
2. they got the same red full color like the others
3. i unify the normals with the "normal" modifier
4. i mirrored some of them in the uv to see if this works but still the same.
where is my problem and what can i do?
cheers
Replies
It's 2019 and I hope it will help.
I basically just had to export the broken mesh from 3dsmax to Zbrush and unwrap it ( I don't know if it's mandatory to unwrap it there ) THEN export your mesh ( that is now fixed ) from Zbrush to 3dsmax and tada ! I opened the UVs in 3ds and polys aren't inverted anymore !
The OP had flipped UV faces and Joost nailed it, way back in 2015. check the orientation of the UV faces and mirror them if they are facing the wrong way. Easy peasey.
If it's a single face within a UV shell, you can detach it, and then target weld each vert to the correct vert.
Sometimes if your UVs double back on themselves it will flag a face as inverted. Relaxing it usually fixes it. Or you can grab the vert and put it somewhere that doesn't cause the face to flip.
If you have just one or two faces that get flipped seemingly randomly, or if your normal map looks all faceted then that is usually an issue with the OBJ importer/exporter, its a pile of garbage and you shouldn't use it if you can avoid it.
OBJ is ancient and hasn't been updated in almost a decade. It continually messes up the winding order of verts, especially UV verts, gets smoothing wrong and fails to calculate normal properly.
Certain operations can cause it to rebuild the vert index table correctly, but it usually rebuilds garbage in a different location. That's one of the main reasons people stay far away from OBJ.
If you're actual faces are turned the wrong way, you'll want to flip them in Edit Poly. This script helps find those backward facing polys and turn them around.
http://www.scriptspot.com/3ds-max/scripts/unify-flip-normal-polygons
Exported the model from Google SketchUp to 3ds max, optimized it well, some did create from zero, but, when creating uv and when using "select inverted polygon", some polygons displayed if they were flipped. Just trying to mirror it in UVWs editor - didn't help. Ok, just trying to detach these polygons and flipping it - the same.
switch UW/VW view, flatten everything in W and see if that resolves it