🧵 Untitled Thread
Anonymous at Sat, 13 Jan 2024 11:14:07 UTC No. 970337
Hi, blender idiot here
I've been slowly making/editing an avatar for vrchat where I had to model legs for a body (the original had stupid furry dog legs) and ever since I've been having a lot of trouble with the weight painting on the knees. I've tried all sorts of stuff, messing around with pretty much everything and I'm clueless at this point. As you can see, the skin pinches outwards at the bone joint and even if I add/subtract weight from either bone, there will still be something like this. Aside from sculpting, how do I solve this?
Anonymous at Sat, 13 Jan 2024 12:39:13 UTC No. 970345
Your knee is not getting wider at the sides. It has lost volume at the top.
Pic related works for me and it (mostly) fixes all the joints at once but only inside Blender. How to export it to VRChat I have no idea. You're going to have to look for very specific tutorials.
The "preserve" vertex group has all the vertices of the mesh with a weight of 0.5 initially but you can manually weight paint over it.
Anonymous at Sat, 13 Jan 2024 13:36:29 UTC No. 970350
>>970337
Hi, another blender idiot here.
I'm not sure what vrchat skeletons are capable of. But the way I do the knee area, is I create an extra helper bone for the kneecap. Well first I would make the thigh and shin bones more centered of the mesh where they join. And then place a small kneecap bone that goes from the joint, to the dead center of the knee part of the mesh. Then parent the knee bone to both the thigh and shin using the "armature" constraint. Because when the knee is parented to bother the thigh and shin, that makes the knee copy rotation 50/50 between the two. Then just paint the knee to make the mesh pop forward. Smooth it all out until it looks right.
Alternatively, if you don't want to make a knee joint, I would still recommend making sure the joint is center of the mesh at the kneed. And then pulling the joint down slightly, so the top of the shinbone is flush with the bottom of the knee's mesh.
Also, there's a pretty sweet looking knee rigging trick in the sticky thread. I haven't used it myself, but it looks good. >>562021
Anonymous at Sat, 13 Jan 2024 13:52:55 UTC No. 970353
>>970350
Do me a favor. Google "how many joints are in the human body". It'll explain to you why any per-joint solution such as "helper bones" will only lead you to insanity.
Anonymous at Sat, 13 Jan 2024 14:05:08 UTC No. 970355
>>970353
That doesnt make sense and you should know better. For one, the human body doesnt use linear blend skinning
Anonymous at Sat, 13 Jan 2024 14:09:14 UTC No. 970356
>>970353
You're kinda right. I've gone down that road of insanity. However, having come back to take a look at more basic rigging solutions, I've found that knee bones are simple and easy to implement. You don't have to create a bone for every part of the body.
Anonymous at Sat, 13 Jan 2024 14:25:21 UTC No. 970359
>>970355
Look at the picture I've posted >>970345. Look at the modifier stack. It mixes both linear and quaternion via a vertex group and the fact that that particular combination of modifier works is no accident.
I had to go dig Blender 2.49 and read a lot of source code to confirm that that was the solution the original Blender developer (the smart ones, not the current "community oriented" ones) envisioned.
Anonymous at Sat, 13 Jan 2024 14:29:38 UTC No. 970360
>>970359
The human body doesnt use dual quaternion skinning either. Its closest known analogy is a FEM simulation
Anonymous at Sat, 13 Jan 2024 14:33:58 UTC No. 970362
>>970360
Yes and technology will get there eventually, however a VRChat avatar doesn't have to be physically and/or anatomically correct. It has to look credible.
Anonymous at Sat, 13 Jan 2024 14:41:21 UTC No. 970363
>>970362
you will never look "credible" when you dont have muscles and bones sliding underneath the skin and fat jiggle and skin wrinkling
Anonymous at Sat, 13 Jan 2024 14:55:21 UTC No. 970366
>>970363
Are you trying to tell me that Filian is not real?
Anonymous at Sat, 13 Jan 2024 15:06:08 UTC No. 970369
>>970366
i have no idea what that is
Anonymous at Sat, 13 Jan 2024 15:08:05 UTC No. 970370
>>970361
I just tried that anons corrective smooth technique, and it does get better results than my knee helper bone. Not that his image is very convincing. But it looks better on my mesh. You probably don't have to do the half preservation step that he took. Maybe just enable preserve volume, and then corrective smooth after that to get rid of the lumpiness.
But if you can't do all that modifier stuff in vrchat, then perhaps, just pull the joint area back. Something like pic related. And blend the area as best you can. The front of the knee will still lose volume, but the outward pinching should go away. At least, that's what's showing in my test.
Anonymous at Sat, 13 Jan 2024 15:15:58 UTC No. 970371
>>970350
>>970370
I did try that a few minutes ago and I can see what you mean, it got worse in some ways and improved a lot in others and started to look like a proper knee bend so I'll definitely have another go at it later. Thanks a lot.
Anonymous at Sat, 13 Jan 2024 15:17:26 UTC No. 970372
>>970363
I'm working on it but simulations aren't for everybody.
>>970369
Filian is a Twitch v-tuber. Check him out because he's a very sane and relaxing persons with a balanced view of the world and he has a pretty good model.
>>970370
The half-preservation is important because it gives you as easy way to control how much volume you may want to gain or lose per joint.