1. A method comprising: calculating position force vectors that describe forces applied to a plurality of bodies; forming a collision matrix and a force vector for pairs of contacting bodies; solving a system of linear equations defined by the collision matrix as the left hand part and the force vector as the right hand part using a bi-conjugate gradient method; updating positions of the plurality of bodies in accordance with a solution to said system of linear equations; and displaying the results of a collision between said bodies.