title: Direct manipulation blendshapes.
abstract: This paper introduces a simple direct manipulation algorithm for the popular blendshape facial animation approach. As is the case for body animation, direct manipulation of blendshape models is an inverse problem: when a single vertex is moved, the system must infer the movement of other points. The key to solving the inverse problem is the observation that the blendshape sliders are a semantic parameterization -- the corresponding blendshape targets have clear, interpretable functions. Distance in "slider space'' is easily computed and provides the necessary regularization for the inverse problem: The change in semantic position is minimized subject to interpolating the artist's direct manipulations. We give empirical and mathematical demonstrations that a single direct manipulation edit is often the equivalent of multiple slider edits, but the converse is also true, confirming the principle that both editing modes should be supported.
authors.affiliation: Victoria University, New Zealand. zilla@computer.org
authors.forename: J P
authors.initials: JP
authors.lastname: Lewis
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Anjyo
mesh_terms: D001696:Biomechanical Phenomena; D003196:Computer Graphics; D003198:Computer Simulation; D005145:Face / Q000033:anatomy & histology*; D005149:Facial Expression; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D025341:Principal Component Analysis