Sketch Abstractions for Character Posing

Abstract

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.