I had to deal with this issue when I wrote the motion vector solution for
the Barnyard film. To get proper realflow motion vectors required a new
motion vector shader as the vectors aren't stored the same on realflow
meshes as for other types of objects such as polygon meshes, NURBS surfaces,
hair, or XSI particles. Because the render settings are so different,
Realflow objects should be rendered separately from all other types of
objects for motion vector purposes. Also, if you tune your normalization
wrong, the vectors will look really screwy.
I did many things differently from lm_2dmv to account for these variances
and improve workflow. One of them was to provide an option to dump the
motion vectors as raw XYZ data instead of normalized RGBA color so tuning
motion vector normalization could be done in a compositor which was faster
(near realtime) and more precise. When dealing with scenes containing many
hair/furred characters or heavy realflow meshes, it was a time saver as the
compositor didn't have to wait for the scene to be reparsed and dumped to
mental ray every time a parameter was adjusted.
Matt
---------------------
Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
Matt.Lind(at)Mantom.net
Date : Fri, 1 Dec 2006
To : XSI(at)Softimage.COM
