Computer Graphics Laboratory ETH Zurich


Sketch Abstractions for Character Posing

F. Hahn, F. Mutzel, S. Coros, B. Thomaszewski, M. Nitti, M. Gross, R. Sumner

Proceedings of the 2015 ACM SIGGRAPH/Eurographics Symposium on Computer Animation (Los Angeles, California, USA, August 7-9, 2015), pp. 185-191
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We propose a sketch-based posing system for rigged 3D characters that allows artists to create custom sketch abstractions on top of a character's actual shape. A sketch abstraction is composed of rigged curves that form an iconographic 2D representation of the character from a particular viewpoint. When provided with a new input sketch, our optimization system minimizes a nonlinear iterative closest point energy to find the rigging parameters that best align the character's sketch abstraction to the input sketch. A custom regularization term addresses the underconstrained nature of the problem to select favorable poses. Although our system supports arbitrary black-box rigs, we show how to optimize computations when rigging formulas and derivatives are available. We demonstrate our system's flexibility with examples showing different artist-designed sketch abstractions for both full body posing and the customization of individual components of a modular character. Finally, we show that simple sketch abstractions can be built on the fly by projecting a drawn curve onto the character's mesh. Redrawing the curve allows the user to dynamically pose the character. Taken together, our system enables a new form of intuitive sketch-based posing in which the character designer has the freedom to prescribe the sketch abstraction that is most meaningful for the character.

author = {Hahn, Fabian and Mutzel, Frederik and Coros, Stelian and Thomaszewski, Bernhard and Nitti, Maurizio and Gross, Markus and Sumner, Robert W.},
title = {Sketch Abstractions for Character Posing},
booktitle = {Proceedings of the 14th ACM SIGGRAPH / Eurographics Symposium on Computer Animation},
series = {SCA '15},
year = {2015},
isbn = {978-1-4503-3496-9},
location = {Los Angeles, California},
pages = {185--191},
numpages = {7},
url = {},
doi = {10.1145/2786784.2786785},
acmid = {2786785},
publisher = {ACM},
address = {New York, NY, USA},
keywords = {character individualization, sketch-based posing},
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