Vertex Weighting with CAT rigs

Tom Ellis · Sep 2010

Is is possible to weight vertices using CAT like you can with Biped in Max?

If so, how?

The options appear to be there; 'include selected vertices' etc but I don't seem to be able to actually select any verts, only edit the envelopes which is ok to a point but there's a few stray verts that I need to fix.

Thanks

Tom Ellis · Sep 2010

Ah I just needed to hit the 'select vertices' checkbox... oops!

Mark Dygert · Sep 2010

Are you using the Physique modifier? Personally I think you should use the Skin modifier. Physique was added with biped in Max4 and hasn't been updated, skin has gotten some major improvements and really blows the doors off physique. They leave physique in there just in case, but hardly anyone uses it.

It does have some nice deformable envelopes but lacks weight painting, and the individual weighting tools are far superior in Skin. For a while I would use physique for the envelopes then convert it over to skin using [SIZE=-1] Juan "Monster" Martinez Physique to Skin script.

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Tom Ellis · Sep 2010

Thanks Vig.

I am using Skin, but rigging is a whole new world for me. I've followed some tuts on it in the past but this is the first time I've worked on a character of my own and it's an absolute bitch to rig.

Would you recommend CAT or Biped, both seem similar in the end but CAT seems quicker to set up, and also is there any way to completely remove weighting from a vert, I just seem to be able to shift the influence in the weight tool but not remove it completely.

Mark Dygert · Sep 2010

THey're both pretty good rigs and almost identical when aligning the skeleton to the mesh.
CAT's strengths mostly come into play when doing different non-bipedal characters, and the way you manipulate the skeleton can have some nice fluid quick results.

Inside of the skin modifier you set the influance to 0, then go to the Advanced Parameters rollout and click "remove zero weights" to clear all the zero'ed out bones from the list(s). It also helps to (before doing any weighting) to set the "bone affect limit" to 3-4 whatever the engine's limit is. That way you don't get a long lists of bones that have to be zero'ed and removed.

Tom Ellis · Sep 2010

Thanks Vig much appreciated.

Is a lot of weight editing usually necessary? In my quest around the web for hints ant tips on Biped rigging all the examples seem to just be like 'add the skin modifier, mess with envelopes for a few seconds and.... all done!'... whereas my mesh looks like crap with a default skin, mildly better with a lot of envelope faffery and then it still needs a lot of weight editing.

I know it probably depends a lot on the mesh but mine isn't anything particularly crazy, just a bipedal human with pants and a jacket on.

Mark Dygert · Sep 2010

For me it normally goes,
Envelope tweaking (I have a custom set of envelopes I load in based on a standard bone structure I use), its most useful in areas like the knees, elbows and hands.
I then load in some animation of extreme poses and check how its deforming.
I then use the paint weights feature (uncheck "Paint with blend weights" to actually paint weights instead of just blend) to smooth out any problem areas.
Ctrl + Shift + LMB Drag = Brush size
Alt + Shift + LMB Drag = Brush strength
Holding alt while painting reverses the strength.

Very rarely do I go in and adjust the weights by hand but every once in a while its needed for a few problem areas.

Tom Ellis · Sep 2010

Ok cheers, I've seen the paint weights tool but it never seems to actually do anything, is there a certain way to set it up? When I activate it and click on my mesh, the cursor changes to the paint tool but doesn't paint anything.

Also, what exactly does 'blend weights' mean?

Mark Dygert · Sep 2010

It defaults to blend weights and if you want to actually paint weights you need to turn that off, its a check box just under the paint weight button. With it on, it attempts to smooth out the area under the brush with a bias toward the selected bone.

When painting you want to use the shortcuts I listed to control the brush size, strength and to reverse the strength. When painting it weights toward the currently selected bone.

Tom Ellis · Sep 2010

Cheers Vig, I seem to be getting it now. One further question though;

How do you comprehensively edit weighting on the spine/head bones? They don't appear in the weighting list and when selecting their envelopes I get crazy results when editing the vertex weights either by painting or editing them in the weight tool.

It seems they are either weighted or not, no gradual weighting. For example, the top spine bone is wrongly weighting some of my characters face/chin and when I rotate the top spine joint it squashes his head.

Obviously this is not what I want but when I try to edit the weighting for that bone, and remove some of the weighting, it shoots his chin down to almost his pelvis.

EDIT: Using the weight tool with multiple bones selected seems to have worked, I am presuming previously I was removing weighting on the chin area from all bones which was causing the craziness. Nonetheless, painting weights still doesn't seem to work on the spine/neck bones.

Mark Dygert · Sep 2010

Yep that happens to me all the time, the top of the torso is normally a mess, don't get me started on shoulders, if you're lucky they don't move around that much =P

For some reason I think it had added the pelvis (or some other undesirable bone) to the weight list for those verts. The skin modifier is probably set to "Normalize" the weights (make sure they add up to 1.0). If you have bones with zero weights and you do something like blend it can start to assign more weight to those zero bones.

You can adjust up the Remove Zero Limit and probably catch a few more of those little .01 bone assignments it likes to do.

Tom Ellis · Sep 2010

Heh ok thanks man, I think I'm getting there with it. For the most part it's looking good, just tidying up those stray weights.

Thanks again.

Vertex Weighting with CAT rigs

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