I have a model I’m exporting from Blender that has 3 blendshapes (in blender called shape keys). In Unity, if the blendshape values sum to 100%, the model looks OK and the resulting mesh shape is the correct blending between the three shapes. However, if the weights don’t sum to 100% the vertices are each offset seemingly at random so that the model becomes a big spiky mess. In blender I can individually move the shape key weights from 0 - 1 and any combination looks OK.
Why is Unity messing up when the weights don’t sum to 100%? Is this a bug, or am I missing some constraint I should know about?
I’ve tried removing the drivers on the shape key values in Blender, and either exporting animations or not exporting animations, all of which give the same result. The same thing happens if I directly use the .blend file asset instead of the fbx exported file. I’ve toggled I think every option under the asset import inspector menu. I’ve also successfully exported a different blender model with 2 blendshapes before without any issue.
To illustrate, here are the screenshots where I’m modifying the blendshapes (which you can see on the right in the inspector). Thanks in advance!
Versions:
Unity 2020.3.22f1
on Linux (arch)
Blender 2.93.5