topic Re: Help with fixing degenerate faces in 3ds Max Modeling Forum

Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 00:24:05 GMT

Okay, so, I'm having a bit of a problem with a few meshes I'm trying to import into my Unreal scene. They either won't load with the rest of model, or if I try to import them separately, it tells me there are degenerate faces. I'm still kinda struggling to wrap my head around what they are as the explanations I've read don't make a lot of sense, but I think I've got the gist of it.

The mesh in question is this:

According to xView > Overlapping Vertices, every vertex is highlighted green (321). I'm not sure how best to fix them. I've tried the Weld tool, but that just crushes everything together, even at the lowest threshold. What would be the best way of tackling something like this?

Re: Help with fixing degenerate faces

BenBisares — Tue, 11 Aug 2020 03:27:09 GMT

Possible to attach an archive (File > Achive) of that scene? From the screenshot I can't see any obvious issues but the fact that you said that welding welds everything together is a bit strange.

Re: Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 10:40:33 GMT

Sure, no problem. I've detached the main culprit as a separate object, but the others have been attached to the rest of the mesh so things all load together as a single object in Unreal.

I've also encountered this issue with other bolts and screws in my Unreal scene...

A lot of the faces are missing! I've tried applying a Normal modifier, resetting the XForm, importing as an FBX or OBJ... I'm guessing this is related to the other issue, except Unreal doesn't give me any warnings about degenerate faces. 😕

Re: Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 11:11:48 GMT

Okay, I've imported the mesh into Maya and gone through all of the options in the Cleanup Tool. It looks like Edges and Faces with Zero Length are highlighted as problems. The problem is, it seems to be everything that's affected. And cleaning it up pretty much collapses/destroys it, similar to Max's Weld Tool. So I'm not sure how best to proceed with it. 😕

Re: Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 13:11:05 GMT

This is getting more and more confusing... Not to mention frustrating. I loaded up my older models of these bolts and screws and imported them into Unreal. And hey-presto... they were perfectly fine. All I've done is added the UVs back onto them, which were also tested in Unreal so the material would work correctly, copied and placed them around where they needed to be, and gave them material IDs. But once they were re-imported back into Unreal, the same problem has happened again - faces missing. There were no warning messages about degenerate faces either. 😞

Re: Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 13:22:40 GMT

And what's even weirder is that I've just tested each stage in turn - imported a screw/bolt with its UV into Unreal = works. Gave it a material ID and imported it Unreal = worked. Attached it to my base mesh, increased the size and placed it at the front where it could be clearly seen = worked. o_O

Re: Help with fixing degenerate faces

10DSpace — Tue, 11 Aug 2020 14:00:38 GMT

@t_smith5

Attached it to my base mesh, increased the size and placed it at the front where it could be clearly seen = worked. o_O

I wonder if the size of your object is causing a problem with the Unreal engine. I say this because the object that was isolated in the file you posted was extremely small by most standards that I am familiar with. This also fits the fact that you have to set the weld threshold to .00001 cm to avoid collapsing the whole mesh and it could also fit with the degenerate faces mesh error.

So I am tempted to believe that your issue here is too small a scale for the model.

Re: Help with fixing degenerate faces

t_smith5 — Tue, 11 Aug 2020 18:52:43 GMT

I'm not sure... Whether big or small, if I have just a few attached, they're fine. If I have all of them, they're broken. So I don't know if it's anything to do with the amount that are attached. They are supposed to be that size, though I have increased some of them, particularly that offender that wouldn't import at all.

I've even tried the smallest amount when welding - .00001, and it says I still have the same amount of vertices. However, I've tried importing it into Unreal and it hasn't given me any errors, so I'm guessing it's worked...?

Re: Help with fixing degenerate faces

10DSpace — Tue, 11 Aug 2020 19:36:13 GMT

@t_smith5

As far as I could tell, you did not have any unwelded vertices in the mesh that was isolated in the file you posted. When you go down to a very low weld threshold and find the threshold value where you get some unwanted collapsing (i.e, verts that are very close but on separate edges that you created) of verts and then the next lowest threshold setting gives no unwanted collapsing of vertices, then you don't have unwelded vertices that are on top of each other.

But that doesn't mean that you don't have unwelded vertices in any of the other meshes. that you are trying to attach together into a single object.

..if I have just a few attached, they're fine. If I have all of them, they're broken. So I don't know if it's anything to do with the amount that are attached.

Usually it is just a 1 or 2 meshes with errors. I don't think it has to do with the number of meshes that you are combining. Max doesn't care how many valid meshes you combine; at least I never found a limit. You can prove this to yourself by making a simple box converting to an editable poly and making multiple copies of it (the same or more than you are trying to combine), attaching them all and then exporting to your game engine in the way you have normally do.