Screw motions for the animation and analysis of mechanical assemblies

Abstract

CAD systems offer a variety of techniques for designing and rendering models of static 3D objects and even of mechanisms, but relatively few tools exist for interactively specifying arbitrary movements of rigid bodies through space. Such tools are essential, not only for artistic animation, but also, for planning and demonstrating assembly and disassembly procedure of manufactured products. Although, any two positions may be interpolated by an infinity of motions, we chose the screw motion for its relative generality and its computational advantages. The paper covers original algorithms for computing the screw motions from interpolated positions and the envelopes of swept regions generated during the motions. We will also discuss why the formulation of a rigid motion in terms of a sequence of screw motions is more advantageous than other more general motion formulations for computing envelopes of swept regions and for predicting collisions.