We describe a framework for the automatic synthesis of biped locomotion controllers that adapt to uneven terrain at run-time. The framework consists of two components: a per-footstep end-effector path planner and a per-timestep generalized-force solver. At the start of each footstep, the planner performs short-term planning in the space of end-effector trajectories. These trajectories adapt to the interactive task goals and the features of the surrounding uneven terrain at run-time. We solve for the parameters of the planner for different tasks in offline optimizations. Using the per-footstep plan, the generalized-force solver takes ground contacts into consideration and solves a quadratic program at each simulation timestep to obtain joint torques that drive the biped. We demonstrate the capabilities of the controllers in complex navigation tasks where they perform gradual or sharp turns and transition between moving forwards, backwards, and sideways on uneven terrain (including hurdles and stairs) according to the interactive task goals. We also show that the resulting controllers are capable of handling morphology changes to the character.

In this paper we describe a physics-based method for synthesis of bird flight animations. Our method computes a realistic set of wingbeats that enables a bird to follow the specified trajectory. We model the bird as an articulated skeleton with elastically deformable feathers. The bird motion is created by applying joint torques and aerodynamic forces over time in a forward dynamics simulation. We solve for each wingbeat motion separately by optimizing for wingbeat parameters that create the most natural motion. The final animation is constructed by concatenating a series of optimal wingbeats. This detailed bird flight model enables us to produce flight motions of different birds performing a variety of maneuvers including taking off, cruising, rapidly descending, turning, and landing.