Exposé : Position-based Skinning for Soft Articulated Characters

Nadine Abu Rumman fera un exposé de ses travaux de recherche le jeudi 12 Mars 2015 à 13h00 dans la salle C434 au Pôle API d'Illkirch.

Titre : Position-based Skinning for Soft Articulated Characters

Résumé : Animating articulated characters such as virtual humans and animals is still a central challenge in computer graphics. In character animation, skinning is the process of defining how geometric surface deforms according to skeletal poses. Modeling compelling and believable skin deformations is difficult and computationally demanding due to the nonlinear inner mechanics of the flesh. Physics-based skinning methods are able to reproduce realistic motions including secondary effects such as jiggling of soft tissues when the character is moving and volume conservation. Despite offering such realistic effects, physics-based simulation requires complex and intensive computations, and thus it is usually avoided in interactive animations. We present a simple and fast skinning method for soft character animation, suitable for real-time applications. The idea is to create a two-layered deformation schema, the result of which approximates the behavior of the skin. For each frame, the skin is first deformed with a classic linear blend skinning approach, which usually leads to unsightly artefacts like the well-known candy-wrapper effect and volume loss. Then we enforce some geometric constraints which displace the positions of the vertices to mimic the behavior of the skin and achieve effects like volume preservation and jiggling. We allow the artist to control the amount of jiggling and the area of the skin affected by it. The geometric constraints are solved using a Position-Based Dynamics schema. We employ a graph coloring algorithm for parallelizing the computation of the constraints. Being based on Position-Based Dynamics guarantees efficiency and real-time performances while enduring robustness and unconditional stability.