Blend shape
Blend shapes are used in 3D animation to interpolate between different sets of geometry. ジオメトリの補完のことを指す
For instance, blend shapes are often used in facial animation to transition between expressions — like a character breaking into a smile or a frown from a neutral expression.
表情から表情の変換で使うので、その文脈でよく使われる
同じものを別のツールでは違う言葉で指す!
公式Docにはannmari説明がないかも