filename : Ozt13.pdf entry : inproceedings conference : SCA 2013, Anaheim, LA, USA, 19-21 July, 2013 pages : year : 2013 month : July title : Differential Blending for Expressive Sketch-Based Posing subtitle : author : A. Cengiz Oztireli, Ilya Baran, Tiberiu Popa, Boris Dalstein, Robert W. Sumner, Markus Gross booktitle : Symposium on Computer Animation ISSN/ISBN : editor : publisher : ACM & EG publ.place : volume : issue : language : English keywords : Skeletal animation, posing, skinning, deformation abstract : Generating highly expressive and caricatured poses can be difficult in 3D computer animation because artists must interact with characters indirectly through complex character rigs. Furthermore, since caricatured poses often involve large bends and twists, artifacts arise with traditional skinning algorithms that are not designed to blend large, disparate rotations and cannot represent extremely large rotations. To overcome these problems, we introduce a differential blending algorithm that can successfully encode and blend large transformations, overcoming the inherent limitation of previous skeletal representations. Based on this blending method, we illustrate a sketch-based interface that supports curved bones and implements the line-of-action concept from hand-drawn animation to create expressive poses in 3D animation. By interpolating stored differential transformations across temporal keyframes, our system also generates caricatured animation. We present a detailed technical analysis of our differential blending algorithm and show several posing and animation results created using our system to demonstrate the utility of our method in practice.