I think I read on the Mental Ray mailing list that it's a problem/bug in the way Maya translates the scene over. *goes and searches* Yep, here:
"maya's approximation editor can do subd approx and/or displace approx. as i
mentioned in an earlier email, the two do not work together correctly. maya
exports these lines:
approximate subdivision surface parametric 2. "Triangles"
approximate displace fine view length 0.25 0 4 "Triangles"
but it should be done in one line like this:
approximate subdivision surface view length 0.25 0 4 "Triangles"
this is because in mental ray 3.3 when the two are used in conjunction "The
displace approximation is ignored, and the regular approximation is used.
Subdivision surfaces are refined during displacement in a single integrated
Is this the last word on using displacements and subdivisions together? any updates on the 6.5 implementation? i would love to be able to use mr's displacement approx as well as rendering subd's.
if anyone knows more than i do... :)