bendy joints

#1

Hello,

I recently discovered that thread:
http://forums.cgsociety.org/showthread.php?t=936746

I have some doubts in the process of dustin and I wonder if it is possible to revisit the issue.

Thanks!

#2

Well, I will begin by recalling the method of dustin:

  1. 3 joint chain setup; 1 FK, 1 IK, and the “Blending” joints that switches back and forth between IK and FK. The “Blending” joints is the joint chain that the character would normally be skinned to, but I created the curve joints for that instead.

  2. 2 NURBS curves; (use the cv or ep curve tool) 1 from the shoulder to the elbow, 1 from the elbow to the wrist.

  3. The 2 curves have 4 CV’s; one at each end, and 2 inner CV’s. Where you place the two inner CV’s is up to you, however I found they worked best closer to the ends than the middle of the curve

  4. For the upper arm curve, there are two clusters. Both are grouped (just for my own sake), the top 2 points’ cluster group has it’s pivot on the shoulder. The other group is on the elbow.

  5. Repeat for the lower arm, and the elbow cluster for the lower arm can share the same group node as the upper arm elbow cluster

  6. The shoulder and wrist cluster groups are parent constrained to the respective “Blending” joints.

  7. The elbow cluster group takes only half the rotation of the elbow. There are a few ways to do this, like parenting the group to the elbow joint, and then setting its rotation to (elbowRotation * -.5) or use aim constraints so it points midway between the shoulder and wrist.

*Now, the curves should follow the “Blending” arm joints and as any of the arm joints are rotated, the curve should bend with joint.

  1. Attach the joints to the curve with motion paths. Delete the keys on the u value, and space them out accordingly. You will also need to create a locator or use some object for the up-axis, to make sure the joints do not flip and pop. This is the main disadvantage of using the curves instead of a ribbon.

  2. For the “ElbowCurve” joint, (the one that is centered on the elbow) should probably be parent constrained to the elbow cluster group. Putting this joint at the very tip of a curve can cause weirdness. Or, just give it a very small value offsetting it from the end.

*DO NOT PARENT THE CURVE JOINTS TO EACH OTHER, because this will cause issues.

  1. Create a custom attribute called “curve” or something, that goes from 0-1. I have this on my IK/FK switch control, because it is the only arm control I have that is always visible. Then connect that channel to the scale of the 3 cluster groups. So if “curve” is set to 0, the scale of the clusters goes to 0, which stacks all the CV’s on the curves at each joint, so there are no points in the middle of the curve, which makes the curve completely straight.
#3

My first doubt is in the steps 4 and 5:

Shoul be the wrist´s cluster group pivot on the wrist blending joint?

#4

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