2PAC: Two Point Attractors for Center of Mass Trajectories in Multi Contact Scenarios

Steve Tonneau (1) , Pierre Fernbach (1) , Andrea del Prete (1) , Julien Pettré (2) , Nicolas Mansard (1)

1 LAAS-GEPETTO - Équipe Mouvement des Systèmes Anthropomorphes
2 RAINBOW - Sensor-based and interactive robotics

Synthesizing motions for legged characters in arbitrary environments is a long-standing problem that has recently received a lot of attention from the computer graphics community. We tackle this problem with a procedural approach that is generic, fully automatic and independent from motion capture data. The main contribution of this paper is a point-mass-model-based method to synthesize Center Of Mass trajectories. These trajectories are then used to generate the whole-body motion of the character. The use of a point mass model often results in physically inconsistent motions and joint limit violations. We mitigate these issues through the use of a novel formulation of the kinematic constraints which allows us to generate a quasi-static Center Of Mass trajectory, in a way that is both user-friendly and computationally efficient. We also show that the quasi-static constraint can be relaxed to generate motions usable for applications of computer graphics (on average 83% of a given trajectory remain physically consistent). Our method was integrated in our open-source contact planner and tested with different scenarios-some never addressed before-featuring legged characters performing non-gaited motions in cluttered environments. The computational efficiency of our trajectory generation algorithm (under ten ms to compute one second of motion) enables us to synthesize motions in a few seconds, one order of magnitude faster than state-of-the-art methods.

Mots clés: Physical simulation; center of mass ACM Reference format:; Character animation; Procedural animation; Additional Key Words and Phrases: Character animation; center of mass; multi contact locomotion; CCS Concepts: • Computing methodologies → Procedural animation; motion planning

Domaines: Multimédia [cs.MM]

Steve Tonneau, Pierre Fernbach, Andrea del Prete, Julien Pettré, Nicolas Mansard. 2PAC: Two Point Attractors for Center of Mass Trajectories in Multi Contact Scenarios. ACM Transactions on Graphics, 2018, 37 (5), pp.176. ⟨10.1145/3213773⟩. ⟨hal-01609055v2⟩