VIPER: Volume Invariant Position-based Elastic Rods

Baptiste Angles (1, 2, 3, 4, 5) , Daniel Rebain (3, 2) , Miles Macklin (6, 7) , Brian Wyvill (2) , Loic Barthe (5, 8) , J P Lewis (4) , Javier von Der Pahlen (4) , Shahram Izadi (3) , Julien Valentin (3) , Sofien Bouaziz (3) , Andrea Tagliasacchi (2, 9, 3)

1 UT - Université de Toulouse
2 UVIC - University of Victoria [Canada]
3 Google Inc
4 Electronic Arts SEED
5 IRIT-STORM - Structural Models and Tools in Computer Graphics
6 NVIDIA - NVIDIA
7 UCPH - University of Copenhagen = Københavns Universitet
8 UT3 - Université Toulouse III - Paul Sabatier
9 University of Waterloo [Waterloo]

We extend the formulation of position-based rods to include elastic volumetric deformations. We achieve this by introducing an additional degree of freedom per vertex-isotropic scale (and its velocity). Including scale enriches the space of possible deformations, allowing the simulation of volumetric effects, such as a reduction in cross-sectional area when a rod is stretched. We rigorously derive the continuous formulation of its elastic energy potentials, and hence its associated position-based dynamics (PBD) updates to realize this model, enabling the simulation of up to 26000 DOFs at 140 Hz in our GPU implementation. We further show how rods can provide a compact alternative to tetrahedral meshes for the representation of complex muscle deformations, as well as providing a convenient representation for collision detection. This is achieved by modeling a muscle as a bundle of rods, for which we also introduce a technique to automatically convert a muscle surface mesh into a rods-bundle. Finally, we show how rods and/or bundles can be skinned to a surface mesh to drive its deformation, resulting in an alternative to cages for real-time volumetric deformation. The source code of our physics engine will be openly available.

Mots clés: soft-body deformation; Cosserat rods

Domaines: Synthèse d'image et réalité virtuelle [cs.GR]

Baptiste Angles, Daniel Rebain, Miles Macklin, Brian Wyvill, Loic Barthe, et al.. VIPER: Volume Invariant Position-based Elastic Rods. Proceedings of the ACM on Computer Graphics and Interactive Techniques, 2019, ⟨10.1145/3340260⟩. ⟨hal-02288948⟩