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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.