View Full Version : twisting mesh

02 February 2006, 06:24 AM
iam a student currently learning maya, for my project i have modeled a character which is muscular and contain hipoly.and iam finished rigging also with influence object.while iam skining the character, iam facing many problem,one is the mesh in forearm is twisting and i dont know how to twist the influence object (for influence object i have used cluster) in the forearm.and in the elbow the muscle is not working properly and my main problem is using a cluster for the influence object.i am also tried adding extra joints inbetween elbow and wrist but its working slightly but iam not able to get the best help me for rigging and skining.(since my project rule doent allow me show the model iam unable to show it)

02 February 2006, 04:37 PM
how are you using the cluster to influence the geometry? If the clusters are just parented to the joints, then they really aren't going to be doing anything (assuming the are relative, which I would imagine they would be). For influence objects, you usually want to use geometry (i use nurbs as they are more smooth), then use set driven keys on them (usually on a CV level) based on joint rotation. Then parent the geometry under the correct Joint, and that will give you good deformations with the influence object.

02 February 2006, 04:10 PM
Yeah, the rotation of the forearm is tough! The thing is, actually we are not talking about one bone but about two: The ulnar and the radius bone. These two are connected two the elbow by the one end and to the hand at the other.

When your wrist/forearm rotates, these two bones go from a paralell position to form something like an x. This is, because they stick to the elbow at the one end and rotate with the wrist at the other. Sounds tough? It is! I have found out that the best way is to mimic the bones setup with a rig is to have these controlled by an extra joint, that is half way between the elbow and the wrist. This joint doesnīt have any influence on your mesh, but it is the driver for a driven key controlling the rotation for your radius and your ulnar (You donīt need a joint, any other helper object attached to your rig will do, I just found this solution handy!). Now your mesh should deform quite nicely, although you might like to use a lattice to support the driven key bone deformation.

Ah yes, and if you are using the FB/IK skeleton, be prepared for problems with the driven keys! :)

Cheers mate...

02 February 2006, 02:02 AM
hi dunkelzahn ,dicotomy

thanks for ur tips man now iam once again rigging the hand but i havent binded the rig.
ill also used a extra joint inbetween wrist and i think ill get the necessary result.

02 February 2006, 08:52 AM
Good luck man, remember this ulnar/radius thing is a bit complicated at the beginning but once you understand it, it sould work quite nicely. Delete your models history before rigging and create a duplicate for the odd blendshape. Might be worth a try for your muscles...

02 February 2006, 03:41 AM
hi dunkelzahn
still iam getting the same result,what i tried is giving setdriven to the extra joint between wrist and elbow thatis when wrist rotates the extra joint has to rotate,but this joint rotation works only in ik/fk half blend mode.and one thing u told about the lattice to support the driven key bone deformation.i dont know how to get that.just give me detailed help on how to over come this problem.r do u use a three joint chain for the arm setup.


02 February 2006, 08:57 AM
Hello again,

this below is a rough joint setup of what Iīd do:

Ulnar End<--Ulnar Root
_________________I <-Connection from Elbow to Ulnar Root
Wrist<--Extra Joint<--Elbow
_________________I<-Connection from Elbow to Radius Root
Radius End<--Radius Root

Now, the "extra joint" drives the rotation of Ulnar and Radius Root around the Elbow, while the Ends rotate WITH the Wrist. That is the trick of this whole human anatomy stuff...

The Lattice will have to be constrained to the proper joint to follow correctly

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