View Full Version : RenderMan 3 - Motion blurring an animated displacement map

10 October 2009, 01:02 AM
Using Maya 2009, I'm trying to figure out if it's possible to motion blur an animated displacement map.

For example, make a subD plane, then put a displacement map (white to black circular ramp) which displaces a cylinder in the center. Now key the place2dTexture node so that it moves very fast across the plane. Problem is... that cylinder is not being blurred even when full 3d motion blurring is enabled.

This was the case for both mental ray and RenderMan 3.01. The displacement is being done before the motion blur calculation since displacements on moving objects are blurred, but not the actual animation of them.

Any ideas?

10 October 2009, 02:02 AM
Thats a pretty interesting question, I'd like to know the answer to that aswell.

Most likely, the problem involves the geomety not moving, thus not creating any motion vectors. Mental ray's motion blur has a "full" or "deform" mode, which takes vertecies into account, but since your cylinder example has the vertecies only moving on one axis, sliding underneat the surface, they wouldn't be an accurate estimation of how the cylinder was actually moving.

10 October 2009, 04:26 AM
Ah yeah, I completely forgot about the motion vectors. If you apply the displacement directly to the vertices before rendertime, the blur will work properly, however, I feel like I'm just missing an obvious step.

Kinda wonder if a shader exists which could take vertices, similar to what the polyMoveVertex command does (Transform Component Tool), and transform them based on the map connected to it. It wouldn't be a rendertime displacement map, but a realtime displacement. I figure a few connections here and there could get the job done. Too curious to sleep (or get other work done) now.

10 October 2009, 12:57 AM
Have a look at the cMuscleDisplace node. It has a realtime displacement feature.

10 October 2009, 08:35 AM
Thanks marcuso!,topicNumber=d0e368476

This seems to be a great workaround.

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