Triangular Lighting Artifacts on Model

[Garlic Bread]

I can't seem to find anyone else with this issue, so I'm gonna make a post for it.

I'm using a custom model, this one specifically: https://steamcommunity.com/sharedfiles/filedetails/?id=870531897
and on her right hand, I'm getting weird triangular lighting glitches.

Example: https://imgur.com/a/K4tmA5A

Unfortunately, I can't seem to find anyone else having this issue, not even on the workshop page.

Could it possibly be an issue with the model itself and therefore be out of my control? I've been racking my brain for an hour now trying to figure this out, so any help would be appreciated.

Thanks!

[Marco Skoll]

This looks like a model issue. I'm currently downloading it to check it myself.

[_MaZ_TeR_]

Normals in those areas are flipped by 180 degrees. Use a model editor to flip them as to how they're supposed to look like.

[Marco Skoll]

Originally posted by _MaZ_TeR_:

Normals in those areas are flipped by 180 degrees.

... thaaaaat's not what it is.

I've decompiled it to check, and it's an utterly insane affair where the entire hand has each of the quads duplicated, which are then triangulated in opposite directions?!

Unfortunately, it can't be just fixed by removing duplicate verts, because of the crossed triangulation. You'd need to either convert it back to quads then remove duplicate vertices, or manually delete a huge number of edges to remove the conflicting faces.

It would be a pain to fix without the original untriangulated files, and the author doesn't seem to be too co-operative about fixing issues.

[Garlic Bread]

Originally posted by Marco Skoll:

Unfortunately, it can't be just fixed by removing duplicate verts, because of the crossed triangulation. You'd need to either convert it back to quads then remove duplicate vertices, or manually delete a huge number of edges to remove the conflicting faces.

It would be a pain to fix without the original files, and the author doesn't seem to be too co-operative about fixing issues.

Ah, alright. Unfortunate, but I think I'll live. Thanks for the help anyways!

[_MaZ_TeR_]

Originally posted by Marco Skoll:

Originally posted by _MaZ_TeR_:

Normals in those areas are flipped by 180 degrees.

... thaaaaat's not what it is.

I've decompiled it to check, and it's an utterly insane affair where the entire hand has each of the quads duplicated, which are then triangulated in opposite directions?!

Unfortunately, it can't be just fixed by removing duplicate verts, because of the crossed triangulation. You'd need to either convert it back to quads then remove duplicate vertices, or manually delete a huge number of edges to remove the conflicting faces.

It would be a pain to fix without the original untriangulated files, and the author doesn't seem to be too co-operative about fixing issues.

Do you have multiple normals visible facing different ways on a single vertice in those glitched areas?

[Pte Jack]

No, the situation is exactly as Marco described it. This was most likely caused by joining objects like the hands on 2 sides of the z axis to a mirrored body (torso, hair, etc) which caused the hands to mirror themselves again on both sides and when the the mirror was applied created the duplicate mesh in both of the hands. The hands were most likely tris when removed doubles was used, the matching verts welded themselve together, but because there were opposing edges in the closed quads, it created double mesh sealed with the weld.

See this picture, I've selected the top layer of faces in the selected band and you can see the under lying faces unselected.

https://i.imgur.com/yFimmMC.png

This is an almost impossible situation to fix quickly, it requires a lot of effort and time to corrrect.

Because there is under lying face poking through the upper face, you can't just paint select the outer faces and invert the selection and delete the duped mesh. Also because verts are welded, making seams to split inner and outer faces doesn't work either. Converting to quads a removing doubles doesn't work either, the duped edges remain after the operation.

This is one of those instance where manual intervention is required and to fix it would take quite a bit of time as both hands are affected by this. There are 4680 verts combined in the hands which create 17,512 edges and 15,716 faces. Just looking at these numbers, you can see there are major problems here.

[episoder]

Originally posted by Pte Jack:

-snip-

https://i.imgur.com/yFimmMC.png

This is an almost impossible situation to fix quickly, it requires a lot of effort and time to corrrect.

-snip-

i had one of those before, too. a hairy one.

in this case, if atleast one entire mesh part is facing the correct way, wouldn't it work to just circle select (like brush) the 'front' faces? i mean, blender does trace and select front facing first.

[Pte Jack]

Unfortunately no, I've tried that. the mesh is too close together and as I said, paint (circle) selecting doesn't work as some of the underlying faces are poking through the upper mesh. This particlular model's hands are a monster. Fortunately it is only the hands that are affected like this. The rest of the model is fine and quite well done. It looks like the author made one tiny mistake when he joined the hands to the torso in the body object. They forgot to apply the mirror to the torso before they made the join.

[Marco Skoll]

I've taken a look at the MMD model it's originally ported from (linked in the description).

Unfortunately, the problem exists on this original too, and isn't something that's occurred in porting (had the the hands on the MMD original been okay, it would been pretty easy to graft them onto the Source model).

[episoder]

okay. i may pick up the work (it's a nice model) and fix it eventually, but i'm kinda off tonight. :)

[Pte Jack]

One of the problems with MMD dolls is that they are usually patchwork of existing models. If someone uses an object that already has the problem in the creation of their doll, it just gets carried on if someone else uses that particular part on their creation if they don't fix it.