Blend Shape
Mesh-deformation key
Also known as: Morph target · Shape key · Blendshape
Definition
A blend shape is a saved mesh deformation that can be applied to the base mesh on a slider from 0 to 100%. The most common use is facial animation: dozens of blend shapes capture mouth shapes (visemes), brow positions, eye states, with the animator dialling a combination per frame. Skinning bones handles body deformation; blend shapes handle the subtle face work that bones can't reach.
In production
Sculpt blend shapes in ZBrush (using Morph Target or Layers), export as named morphs, and import into Maya or Blender where they're wired into a blendShape node or Shape Key stack. Modern AAA pipelines have moved toward FACS-based libraries (50+ shapes mapped to specific facial muscles, such as AU12 for the lip-corner-puller) for photoreal characters, following the system originally built for film facial capture. Unreal Engine 5's MetaHuman framework ships with a standardized ~800-shape rig so studios can share facial animation across characters without re-sculpting. A key technical constraint: all blend shapes must share identical vertex order and count with the base mesh, or the import fails or corrupts silently — a frequent bug when an artist re-triangulates the base mesh after shapes were already sculpted. Combination shapes (e.g., "jawOpen + smile") are also authored separately to fix corrective deformation that linear blending alone can't capture around the mouth corners.
