Hasta La Motion!

For a commercial job we want to blend a 3D simulation of an avalanche to a matte painting. But to make the transition smooth we want to analyze the motion of the rendered simulation and offset/distort the mattepainting accordingly for a few frames before it stops and the picture is 100% matte-painted still.

So we need a tool/technique/trick/plugin to analyze the motion, much like any motion blur plugin will do, and generate a displacement map, st/uv-map or whatever from it to distort the final result.

The 3D guys are trying to get a motion vector pass from it, I figured this might help, but it’s not sure that’ll work.

I don’t expect any approach will generate a clean result, but I hope for a good basis to paint on top…

Hopefully my question makes sense, since it’s hard to explain.

Thanks