This paper describes algorithms for the animation of men and women performing three dynamic athletic behaviors: running, bicycling, and vaulting. We animate these behaviors using control algorithms that cause a physically realistic model to perform the desired maneuver. For example, control algorithms allow the simulated humans to maintain balance while moving their arms, to run or bicycle at a variety of speeds, and to perform a handspring vault. Algorithms for group behaviors allow a number of simulated bicyclists to ride as a group while avoiding simple patterns of obstacles. We add secondarymotion to the animations with springmass simulations of clothing driven by the rigid-body motion of the simulated human. For each simulation, we compare the computed motion to that of humans performing similar maneuvers both qualitatively through the comparison of real and simulated video images and quantitatively through the comparison of simulated and biomechanical data.

We introduce a novel algorithm for transforming character animation sequences that preserves essential physical properties of the motion. By using the spacetime constraints dynamics formulation our algorithm maintains realism of the original motion sequence without sacrificing full user control of the editing process. In contrast to

Sensor-actuator networks (SANs) are a new approach for the physically-based animation of objects. The user supplies the configuratíon of a mechanical system that hás been augmented with simple sensors and actuators. It is then possible to automatically discover many possible modes of locomotion for the given object. The SANs providing the control for these modes of locomotion are simple in structure and produce robust control. A SAN consists of a small non-linear network of weighted connections between sensors and actuators. A stochastic procedure for finding and then improving suitable SANs is given. Ten different creatures controlled by this method are presented.

We present a physics-based system for the guided animation of articulated figures. Based on an efficient forward dynamics simulator, we introduce a robust feedback control scheme and a fast two-stage collision response algorithm. A user of our system provides kinematic trajectories for those degrees of freedom (DOFs) of the figure they want direct control over. The output motion is fully generated using forward dynamics. The specified motion trajectories are the input to a control system which computes the forces and torques that should be exerted to achieve the desired motion. The dynamic controllers, designed based on the Model Reference Adaptive Control paradigm, continuously self-adjust for optimal performance in trajectory following. Moreover, the user is given a handle on the type and speed of reaction of the figure 's controlled DOFs to sudden changes in their desired motion. The overall goal of our system is to provide a platform for generating and studying realistic, user cont...

We propose a new method of automatically finding periodic modes of locomotion for arbitrary articulated figures. Cyclic pose control graphs are used as our control representation. These specifically constrain the controller synthesis process to only those controllers producing periodic driving functions. It is shown that stochastic generate-and-test techniques work well with this representation. Several choices that arise in this synthesis technique are explored. The impact of the design of the physical models upon the motions produced is examined. Lastly, the motions produced are analysed by looking at their bifurcation diagrams. Keywords: animation, control, simulation, locomotion, modelling, limit cycles Résumé Nous présentons une nouvelle méthode permettant de trouver automatiquement des mouvement periodiques pour des figures articulées. Nous utilisons des réseaux cycliques de poses pour représenter et contrôler les mouvements. Ces réseaux contraignent la synthèse des contr ôleu...

We extend an earlier automatic motion-synthesis algorithm for physically realistic articulated figures in several ways. First, we summarize several incremental improvements to the original algorithm that improve its efficiency significantly and provide the user with some ability to influence what motions are generated. These techniques can be used by an animator to achieve a desired movement style, or they can be used to guarantee variety in the motions synthesized over several runs of the algorithm. Second, we report on new mechanisms that support the concatenation of existing, automatically generated motion controllers to produce complex, composite movement. Finally, we describe initial work on generalizing the techniques from 2D to 3D articulated figures. Taken together, these results illustrate the promise and challenges afforded by the controller-based approach to automatic motion synthesis for computer animation. CR Categories: I.2.6 [Artificial Intelligence]: Learning---paramete...

Teaching simulated creatures how to walk and run is a challenging problem. As with a baby learning to walk, however, the task of synthesizing the necessary muscle control is simplified if an external hand to assist in maintaining balance is provided. A method of using guiding forces to allow progressive learning of control actions for balanced locomotion is presented. The process has three stages. Stage one involves using a "hand of God" to facilitate balance while the basic actions of a desired motion are learned. Stage two reduces the dependence on external guidance, yielding a more balanced motion. Where possible, a third stage removes the external guidance completely to produce a free, balanced motion. The method is applied to obtain walking motions for a simple biped and a bird-like mechanical creature, as well as walking, running, and skipping motions for a human model of realistic proportions.

The motion of a human platform diver was simulated using a dynamic model and a control system. The dynamic model has 32 actuated degrees of freedom and dynamic parameters within the range of those reported in the literature for humans. The control system uses algorithms for balance, jumping, and twisting to initiate the dive, sequences of desired values for proportional--derivative servos to perform the aerial portion of the dive, and a state machine to sequence the actions throughout the dive. The motion of the simulated diver closely resembles video footage of dives performed by human athletes. The control and simulation techniques presented in this paper are useful for providing realistic motion for synthetic actors in computer animations and virtual environments and may someday be useful for analysis of sports performance. 1. Introduction In this paper, we explore dynamic simulation as a technique for generating animations of an Olympic sport, platform diving. The simulated diver ...

In striving to construct higher level control representations for simulated characters or creatures, one must seek flexible control representations to build upon. We present a method for the synthesis of parameterized, physics-based motions. The method can be applied to both periodic and aperiodic motions. The basis of the method is a low-level control representation in which linear combinations of controllers generally produce predictable in-between motions.

In this paper we describe an animation of a human platform diver. We simulated the motion of the diver using a dynamic model and a control system. The dynamic model is a 32 degree-of-freedom rigid body model with dynamic parameters similar to those reported in the literature for humans. The control system uses algorithms for balance, jumping, and twisting to initiate the dive, proportionalderivative servos to perform the aerial portion of the dive, and a state machine to sequence the actions throughout the dive. The motion of the simulated diver closely resembles video footage of dives performed by human athletes. The combination of dynamic simulation and a control system allowed us to animate the diver using high level commands. The control and simulation techniques presented in this paper may be useful for analysis of sports performance and for providing realistic motion for synthetic actors in computer animation and virtual environments. Keywords: Human Figure Animation, Simulatio...