Blender Rig wrist twist problem.

MrBFox

Hello, a Maya rigger here, been struggling recently with rigging in Blender. been having problems trying to set up a wrist twist with a single bone for a game rig, the current set up I have is with it parented under the wrist bone and aim constrained to an empty at the tip of the upper arm joint and a copy Y rotation constraint, works well enough in the bind pose, but anything involving moving the IK pole vector controls leads to some very unnecessary collapse for forearm geometry. And any searches iv'e done mostly turn up results involving Rigify. Any suggestions?

Frankie

It calculates the constraints from the top of the list to the bottom so why not use two copy rotation constraints on the forearm twist bone? First one copy constraints from the forearm set on all axis at 1 influence then a second set on Y only at 0.5 influence to copy constraints from the hand. 

Problem with this one is automatic weights wont be as good as a two forearm bones in a chain.

(edit) whoops didn't test it properly and it doesn't work, I need this working too. Will let you know if I figure it out

lkruel

I had to deal with this this past weekend, make sure the space on the copy rotation constraint is set to local > local. 

Frankie

Mind posting an example LKRUEL?

Frankie

Hows this, twist bone parented to hand with IK chain setup to forearm bone. Copy rotation getting local Y value from hand at 0.5 and hand and twist bone set to Euler YXZ to evaluate Y first 

https://dl.dropboxusercontent.com/u/1693140/Arm_multi_bone.blend
(Initial rig/model is not mine, found it on blend swap or a forum while looking for examples of forearm twisting and then modified it to work)
Feedback would be good. After reading your post I noticed my previous twist rigs didn't twist when the IK pole was moved, would really prefer the twist bone to be in a chain between the upper forearm and the hand.

If you're using unity please take a look at my other questions here http://polycount.com/discussion/161664/mecanim-questions-clips-not-updating . Feels like it's got lost with the new forum updates being harder to navigate and see whats new.

MrBFox

The current setup I seem to be having some luck with is Axis Angle and locking the W,X,Z axis, parented to wrist (with inherit rotation turned off) with a copy rot on all axis (with invert turned on for X and Y) plus offset and influence of .5 and space set to local local, and damped track constraint on y axis to an empty parented under the upper arm but position at the start of the forearm joint.


I would prefer to have the infinite wrist turn effect I could get  with a maya set up but this way seems to work for now.

Frankie

I would be interested in seeing an example of that setup if you wouldn't mind uploading? I think my setup doesn't work well, at least in that blend file I uploaded.
You might be able to get infinite wrist twist using Transformation constraint and extrapolate while keying with euler, doubt it will work rotating past -180 or 180 in the viewport as it seems to loop round.