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Transposition Based Blendshape Direct Manipulation

Çetinaslan, C. ; Lewis, J. ; Orvalho, V.

Transposition Based Blendshape Direct Manipulation, Proc International Conf. on Computer Graphics Theory and Applications - GRAPP, Porto, Portugal, Vol. ., pp. . - ., February, 2017.

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Abstract
The blendshape approach is a predominant technique for creating high quality facial animation. Facial poses are generated by altering the corresponding weight parameters manually for each key-frame by using traditional slider interfaces. However, authoring a production quality facial animation with this process requires time-consuming, labor intensive and iterative work the artists. Direct manipulation interfaces address this problem with a “pin-and-drag” operation inspired by the inverse kinematics approaches. The mathematical frameworks of the direct manipulation techniques are mostly based on pseudo-inverse of the blendshape matrices which include all target shape’s vertex positions. However, the pseudo-inverse approaches often give unexpected results during the facial pose editing process because of its unstable behavior. To this end, we propose the transposition approach to enhance the direct manipulation by reducing unexpected movements during weight editing. Our approach extracts the deformation directions from the blendshape matrix, and directly maps the sparse constrained point movements to the extracted directions. Our experiments show that, instead of psuedo-inverse based formulations, transposition based framework gives more smooth and reliable facial poses during the weight editing process. The proposed approach improves the fidelity of the generated facial expressions by keeping the hazardous movements in a minimum level. It is robust, efficient, easy to implement and operate on any blendshape model.