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Abstract

Though ray tracing has recently become interactive, its high precomputation time for building spatial indices usually limits its applications to walkthroughs of static scenes. This is a major limitation, as most applications demand support for dynamically animated models. In this paper, we present a new approach to ray trace a special but important class of dynamic scenes, namely models whose connectivity does not change over time and for which the space of all possible poses is known in advance. We support these kinds of models by introducing two new concepts: primary motion decomposition, and fuzzy kd-trees. We analyze the space of poses and break the model down into submeshes with similar motion. For each of these submeshes and for every time step, we calculate a best affine transformation through a least square approach. Any residual motion is then captured in a {\bf single} ``fuzzy kd-tree'' for the entire animation. Together, these techniques allow for ray tracing animations {\em without} rebuilding the spatial index structures for the submeshes, resulting in interactive frame rates of 5 to 15 fps even on a single CPU.