  Debris disk images show clumps, rings, warps, and other structures, many of
which have been interpreted as perturbations from hidden planets. But so far,
no models of these structures have properly accounted for collisions between
dust grains. We have developed new steady-state 3D models of debris disks that
self-consistently incorporate grain-grain collisions. We summarize our
algorithm and use it to illustrate how collisions interact with resonant
trapping in the presence of a planet.
