Blendshapes not deforming correctly

[JHburton1]

Hey everyone,

I'm having a weird issue I was hoping someone could help me with.

I'm doing corrective blendshapes for a joint based facial rig, and I'm having an issue where the corrective blenshape is deforming the mesh in an unexpected way - basically, it modifies some verts that aren't suposed to be moving.

I should point out that the "rogue" verts that are modified are always the same ones, in exactly the same way, regardless of the blendshape applied. 

I've attached some images to help understand the issue a little better (note that I used an example that would be very obvious and not an actually usable deformation!).

As you can see I highlighted the verts that shouldn't be moving, but do so when I apply the blendshape. The SAME verts move regardless of the blendshape mesh i apply 😞

In terms of the deformation order I'm using, it's set to "front of chain" - interestingly, the rogue verts are only affected when I use this method - if I use "default", the issue doesn't occurr, however I can't use this method since when it is used to correct an already deformed mesh (ie: to correct an open jaw), it deforms it back to the full corrective difference pose.

Can anyone help me out with this? 🙂

[s_ehrenhaus]

That could be because when you duplicate your base mesh out for making a blendShape, you have actual stuff going on in its tweak node.

Try turning the tweak node envelope off and see if it actually deforms those verts too. If so, select all verts and zero their transforms out using the CVs tab in the channel box.

Youll basically have to retarget your existing shapes with the fixed vertex positions..

Theres many ways to do that..

One would be to create a blendShape with no edits, that should then still deform your main mesh with those foul verts.. And apply one of your actual blendShapes, and the no edit shape with the inverse value, thus negating the wrong movement.

Then just duplicate that out, and use that as the new clean shape target mesh.

[JHburton1 · Accepted solution]

Hey s_ehrenhaus,

Thanks a lot for your reply - The tweak node wasn't the issue but I managed to fix it - however your response will probably save me a headache in the future so thanks for posting such a detailed solution!

I managed to fix the issue by using the default blendshape mode and then accessing the mesh's inputs stack (in case anyone has the same issue -> select mesh, right click - Inputs - All Inputs) and moving the blendshape node above the skin cluster.

Thanks again for your reply!

James