Need help with corrective blendshape deformations workflow

#1

I have a character ready for animating.
I painted the weights and added a few influence objects to help add shape where I want.
But when I rotate the arm in Y so it is facing out forward, the shoulder vertices get messy.

I am unsure how to proceed.
I already have a blendShape1 node for facial blendshapes I made at the time of initial rigging.

I have cmuscle for the biceps and legs

The character’s bind pose is a T pose.

So if I want to create a corrective pose for the arm when the shoulder is rotated foreward in Y
how do I set it up so the vertices will move into the correct place but not make the arm go back into the T pose?

I tried making a positive and negative duplicate of the t pose and altering the shoulder area blindly where the vertices should go then duplicating the blendshape deformed original and making a new blendshape from that with parallel active
but it didnt work–the arm went back to a t pose as the shoulder area deformed.

I tried turning the character’s shoulder in Y and then creating a duplicate and altering that but it didnt work either.

Could it be a stacking issue? I am confused.
Need help on correct steps. Thanks.

#2

I think I will use a wrap deformer instead.

#3

The good old Comet poseReader can be used to cintrol a blendshape, if you can’t use the poseDeformer. There’s even a python version, somewhere.

Getting the corrective shape is tricky. Without the poseDeformer, you may have to find a script to extract the correction. In my experience, subtracting the uncorrected mesh gives you a shape that only works for that specific (full-body) pose, in parallel mode.

If nothing else, you could also try adding an extra joint or two to the shoulder, to help even out the deformation. Having additional manual control over these could also let you reshape the shoulder as needed.

Hope this helps!

#4

Thanks for the explanation! An extra joint or two would probably help although I goofed when making the mesh because it is one or two edge loops short around the shoulder. If I can add some more without the mesh exploding that may make the deformed area less of a problem.

Although a good old fashion influence object may be useful too.

#5

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