4. The method of claim 1 , further comprising repeating said receiving input representing one or more external forces acting on the animated character, said determining a pose for the animated character in reaction to the one or more external forces, and said displaying the animated character in its determined pose for one or more additional animation frames.
1. A method, comprising: using a computer to perform operations comprising: receiving input defining a trajectory of an animated character as a goal constraint during execution of an interactive application; receiving input representing one or more external forces acting on the animated character during execution of the interactive application, a root of the animated character being unactuated by the one or more external forces; determining a reference pose for the animated character in a current animation frame in reaction to the one or more external forces, said determining comprising performing a quasi-physical simulation, the quasi-physical simulation being expressed as a linear system enforcing the goal constraint for the horizontal components of a center of mass of the animated character by performing operations comprising: determining joint torques to minimize an addition of a non-physical force at the root of the animated character, the joint torques being determined based on a torque objective; determining the non-physical force to apply to the root of the animated character to enforce the goal constraint, the determining the non-physical force not being constrained by the laws of physics simulated in the quasi-physical simulation and the goal constraint being expressed as a linear function of joint accelerations; adding the determined non-physical force to the root of the animated character; and displaying the animated character in its determined pose.