in short: vertices are affected by bone rotations which have no influence in that area-at all… really…
It’s not the first time I encounter with this, it’s connected with rigify somehow and I just can’t understand it.
In the attached file rotating the hand ik bone will rotate the wrist… however the wrist deform bone which is the only bone that has influence there is not moving I actually deleted all other vertex groups to pin point the problem, but I couldn’t…
And this is not only at the hand: what I see is that somehow the children bones have influence on their parent’s vertices (not the parent bone itself)
Please help for the sake of my sanity help me figure out what’s going on ,
THX
Im not sure how you parented or added weights but the hand/fingers were not included. You also need to orient the roll of the bones properly. I have not changed the roll but just checked to see if I could parent and assign weights… works fine. Look up rigify rig on youtube for help with bone orientation.001test.blend (2.9 MB)
go to about the 17 minute mark on this vid and it will explain all you need to know…
I doesn’t work well. I mean, ideally the wrist area should rotate a bit with the hand… that’s why we use twist bones… but there is no twist bone in this scenario… yet the wrist (lower arm) still rotates.
I made a very crude weight painting just to demonstrate the effect.
Thing is: only the lower arm bone has any weight on the arm. The bone is not moving when I rotate the hand, but the lower arm mesh vertices are still affected somehow.
My goal is to modify the rigify rig to my needs… but I can’t do it if there are unexplainable behaviors like this.
Your bones are not oriented properly. The rig will not deform as expected because of this. The finger bones and arm bones need to have the Z axis oriented correctly. My example was only to see if I could parent and weight paint. Im sure if you orient correctky it will resolve your problem.
Sorry, but this doesn’t answer my question. The bone orientations are coming from rigify unmodified.
What I did: created a rig from the metarig with single segmented limbs… so without twistbones… I wanted to give it a different twist bone later. But the lowerarm still behave as it had twistbone or something.
I deleted all vertex group from the mesh to pinpoint the problem… (I painted back the influence for the lower arm bone). (I als odeleted other parts of the model to make the file lighter)
As of right now only the deformation of the lowerarm bone should move the arm, yet rotating the hand still affect the lowerarm portion.