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Direct Manipulation Blendshapes
July/August 2010 (vol. 30 no. 4)
pp. 42-50
J.P. Lewis, Weta Digital
Ken-ichi Anjyo, OLM Digital
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.

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Index Terms:
blendshape, facial animation, direct manipulation, inverse kinematics, computer graphics, graphics and multimedia
Citation:
J.P. Lewis, Ken-ichi Anjyo, "Direct Manipulation Blendshapes," IEEE Computer Graphics and Applications, vol. 30, no. 4, pp. 42-50, July-Aug. 2010, doi:10.1109/MCG.2010.41
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