Strange deforming geometry

Hi, I’ve been using blender for some time now and i have encountered a strange bug that causes geometry to deform in strange ways. the model is rigged and weight painted. any help would be appreciated. thanks! (edit: I was using blender 2.93 when the model stopped working and as far as I can tell whatever caused the weights to bug out has been fixed or it was something on my end.)

Upload blend file so we can say whats wrong with your rig. It may be weight paint problem or problem with armature - wrong bone parenting, or missing deform options on specific bones. And so on.

what’s the best way of uploading it? google drive?

Use any service you like. GD would be ok. there you go. the weight painting is pretty much all automatic so I’m not sure why it’s messed up. also sorry for the poor quality of the model most of its rough edges are hidden by a fur shader in UE4

If we enter weight paint and look at one of these verts, we can see that it has some very weird looking weights:

“nan” means not a number; the most common way of getting a “nan” is dividing by zero. Most of the time, Blender will evaluate this as the largest possible floating point value, which will totally break everything. Here, you should just lasso select all those verts in weight paint and remove from both of these broken vertex groups, because they shouldn’t be in those vert groups at all anyways.

Now, how’d that happen? I couldn’t tell you. There isn’t anything obviously enough wrong with the mesh to imagine Blender choking on it. (There are a couple of non-manifold verts, but they’re not important verts, nor anywhere near this.) When I reweight your mesh with autoweights, in 3.01, it doesn’t reproduce.

First potential cause would be any scripting. Second would be any addons. If you’re not scripting, and you’re not using any third party addons, and your computer wasn’t struck by a cosmic ray or something, then it’s a bug in Blender, and if you can reproduce it, it would be worth going on the bug tracker.

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Here is quick fix for bad weighted vertices.

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yeah the model is rough but I don’t have any scripting or addons, the mesh was just like that after i tried to clean up the auto weight on the eyes but I haven’t used the weight painting tools in blender before so who knows. thank you for your time though!

TBH weightpainting workflow in blender after 2.79 looks to me almost broken and unituitive. So much options are scattered in different places. Mirror weightpainting is also seems to me broken. After small adjustment of mesh with smooth brush in sculpt mode you have big chance to find out that mirror weights on some vertices aren’t working anymore. In 2.79 it was way better IMHO.

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