topic Please Help Me Skin a Biped in a Way that isn't horrifying! in 3ds Max Animation and Rigging Forum

Please Help Me Skin a Biped in a Way that isn't horrifying!

tfairfield4 — Sat, 14 Oct 2017 00:02:55 GMT

Be warned; this way lie some rather disturbing images of a leg contorting in an unnatural way.

So, I've made a a biped character; somewhat chibified, and I've rigged up all the bones. Now comes the skinning process, and somehow, I haven't been able to get the knees to look good when bending. In fact, instead of bending, the knees stretch. Here come the pictures. First how the leg looks straight.

Now brace yourself for what happens when it bends:

The knee contorts to cover more of the leg, looking rather creepy.

I want to mention, here, that this is actually my second try with skinning leg bones. The first time, I made a thigh and calf bone combination that intersected roughly in the middle of the knee; this happened back then, too. So I made new legs, rigged them up so that the calf began under the knee. It's still happening. In other words, after trying two different things, I'm not so sure how to fix it. If it helps you out when answering, here's a shot of the envelope editing:

I'm not sure which vertices to include or exclude to make the knee stop doing that. Chances are that the culprit could be the bones, rather than skinning envelope, in which case I'd have to redo the bones, but since last time I did that it didn't work, I would need to know the right way to do it this time. Please advise, on whatever can right this wrong.

Re: Please Help Me Skin a Biped in a Way that isn't horrifying!

har1sf0x — Mon, 16 Oct 2017 10:56:48 GMT

Hello,

From your sayings it seams that your second approach is the most problematic in my opinion. The knee joint must be in the right place, as it was as you say in your first attempt. Skinning should be the problem. Skinning is not an easy task to do and envelopes is not the best way to do it, it is just a rough approximation. You should check the vertices methods such as paint weight, weight table e.t.c. There are several tutorials from Autodesk and others (e.g. paulNeale ).

Best of luck,

har1sf0x

Re: Please Help Me Skin a Biped in a Way that isn't horrifying!

tfairfield4 — Wed, 18 Oct 2017 00:23:35 GMT

I thank you for those linked videos; I will look into them. First, though, some quick questions:

1) In general, is the "right place" to put a knee (on the skin) half on the thigh bone and half on the calf bone?

2) Should the vertices that make up a knee likewise be divided between the thigh bone and calf bone, depending on which position they conform to? Or should they all be bound to one bone? Or should some vertices conform to multiple bones? Or are all of these things useless in fixing joints to look right?

I also came to the conclusion that envelopes aren't a very precise way to bind skin to bones, selecting vertices manually is better, and I'm increasingly proficient at doing this, but exactly how I should use manual selection of vertices to fix this problem, remains unclear.

Re: Please Help Me Skin a Biped in a Way that isn't horrifying!

Anonymous — Wed, 18 Oct 2017 10:02:08 GMT

Hello tfairfield4,

skinning can really be annoying, but if you gain some practice and experience you will be able to identify problematic spots and place the joints properly. Concering the proper position of the knee-joint it is hard to tell if it is placed correctly in your rig, but it is best if you just move the joint to different locations and judge for your own. To do so, you do not need to reskin the mesh - just deactive "Always deform" in the "Advanced Options" rollout of the modifier, shift your joint and activate "Always deform" again. Hopefully your rig is still in T-Pose and not scaled, otherwise you might not get what I descripted.

Concernig the weighting of the verts I can advise you to use the "Weight Tool" - you'll find it in the panel of the modifier. You can "blend" the weight of selected verts between bones with this, add weight, multiply weight and copy weights. With some practice you will get a smooth skinning quiet fast. Check the MaxHelp for angle-deformations with the skinmodifier. With such a "fat knee" you will have to morph the skinned geometry depending of the angle of thigh and calf to get a convincing result.

Check the topic "Dual Quaternion" in the Helpfiles - this might give you more informations about how to achive a good skinning on joints.

Best,

Martin

Re: Please Help Me Skin a Biped in a Way that isn't horrifying!

tfairfield4 — Sat, 28 Oct 2017 23:30:18 GMT

So, thanks for all the help so far, and I've made good progress on the knees. But now what I'd like to know is, is there a way to prevent portions of the skin from phasing into one another? This is a big issue during things like bending knees; the bulges on the back of the thigh and the back of the calf go through each other like ghosts; of course, there are plenty of other examples. I think I might have seen some reference to other modifiers that make skin deform more realistically; but I'm not sure what they would be. One would think the modifier called Skin would have the ability to behave like real skin, but I'm not sure how.