Tips on fixing Butt deformation

TorQue[MoD]

Hey guys!

As you all know, using a rigid physique on a low poly character model can often cause some really bad deformation in the anterior regions of your model... I was just wondering if anyone has any tips or knows of any tutorials on dealing with this? I looked around on the net for a while and didn't find anything.

I can usually manage to get deformation of my models down to a few minor stretches here and there when it comes to the shoulders, but for some reason I have yet to figure out how to properly set up a model's butt so it doesn't deform so much that it looks like he's wearing an oversized diaper that hasn't been changed for a year.

For example:


Sorry that I can't show the entire model... NDA.

But as you can see, this butt has some serious deformation problems. I can't seem to figure out what links are the best choice to assign the butt vertices too. If I assign them to one area of the model, the butt looks fine while standing, but looks horrible while crouching (as you can see here). If I make it look good when he's crouching, it looks bad standing.

Also, does anyone know if Quake 3 supports blended vertice assignment or only rigid? maybe that would help.

I'm still new to character rigging so any help is greatly appreciated.

Oh yeah, running Max 4.2

Thanks!

JonMurphy

Quake 3 used morphing meshes, so you could use blended verts. That is, unless you are working with the engine and have access to the skeletal stuff. Even then, you should be allowed 2-3 rigid bone influences per vert.

I find a balanced blend between the thighs and the pelvis work. Less thigh influence on the butt as opposed to the front of the pelvis, which has more thigh influence.

Eric Chadwick

Helps me to use an animation of a person going through calisthenics, and weight to that.

TorQue[MoD]

How do you weight to an animation?

Yeah, I tried switching between the thighs and lower pelvis, but this didn't fix anything. I guess I'll try to see if a blended assignment will make enough of a difference.

Ayone know of any useful rigging tutorials?

Thanks!

Snowfly

I think EricChadwick is refering to loading a mocap file to a Char Studio Biped, and test weighting the model in all ranges of poses. You could just as well make up your own animation and tweak the weights around that. Efficient way of working...

Also wanted to point out that a lot of deformation problems can be solved with good topology. So if you can't redo the layout of your character's butt, at least figure something out for use on your next model.

Is it ok to show a wireframe of the butt area? And the joint placement?

Eric Chadwick

Yes, that's what I meant. I used to use a mocap Bip file, but now I just animate a quickie set of motions when I make a new skeleton.

Here's a rigging tutorial for max 4, from the Joan of Arc tutorials. Uses Skin not Physique, but the principles are the same. Don't miss the section starting at part 5 page 2/5. Some nice illustrations of how he massages the ass (so to speak).
http://babelfish.altavista.com/babelfish...ing_base_01.htm

TorQue[MoD]

Here's a pic of the model's butt with the absolute worst deformation. I've never had a model with deformation as bad as this, so I'm thinking it might be the model itself rather than my rigging abilities. All of the vertices in his but right now are linked to the upper right hip.

If I try assigning even one to the lower pelvis it horribly distorts. Maybe the problem is that I didn't pay enough attention to sizing the biped to the character or something?

Anyway....



Also, something else that I've never seen in a model is the butt region also flares out like a parachute catching wind at one point during the animation. And even when I rotated every biped part, it doesn't seem to affect the butt area of the model.

I'll probably just start over with this one. Max might be acting goofy.

TorQue[MoD]

So I tried assigning the vertices to the skeleton with a deform assignment instead of rigid, and this fixes a lot of the deformation problems, but I can't seem to tell some areas of the mesh to be assigned rigidly. The chin for example if blended between the head and neck biped where I only want it assigned to the head. So I select those vertices, switch to rigid and assign them to the head biped, but they still remain blendedly assigned.
I tried removing them from the neck and head links and assigning them rigidly again but this didn't work either.

Is there some trick to assigning vertices rigidly once you've selected blended or can you only do one or the other?

I also chose Nlinks for the type of assignment. Should I have chosen 2, 3 or 4 links?

Thanks again!

KDR_11k

I think you need to unlink them from the jawbone instead of assigning them to the head again.

TorQue[MoD]

There isn't a jaw bone in my setup, the head link is the only one.

But I figured it out. I must have been tired last night cause I completely missed the drop down menu for selecting the blending type of the vertices.

KDR_11k

Ah, oops, I misread neck as chin. Anyway, that was just an example.

Slash

Dont worry if you cant get it perfect. Just look at the doom3 dude in thirdpersonview while crouching!

Scott Ruggels

Rigging Butts on models is something you just have to work at. some models need an extra bone in each cheek to control the collapse. In others, you have to make sure everything is anatomically perfect, in terms of bone axis placement, and with careful weighting you get a nice deformation and movement. At some point however, engines will have to allow for deformers and perhaps blandshapes to control movement deformations, and even mouthshapes eventually . HL2 does this, but apparently is way too hard to implement unless you Own XSI.

Scott

Rakile

When I'm using Character Studio, I usually end up locking the verticies in problem areas and then manually typing in the weights. For example, with the butt, I'd try adjusting the wieght between the thigh and pelvis, and when it looks good in one position, move the leg, and see if it works. I hope that made sense...