Motion blur and alembic instances

[simon.ekeberg]

Hi!

I'm trying to render alot of debris simulated in Houdini.
Each debris particle has an instanced gravel geometry which I export out as alembic instances (packed geometry in Houdini). My problem is getting motionblur to work with these. I am supplying a velocity vector for each instance point which looks correct in Houdini but won't produce any motionblur in vray.

I have no problem getting motionblur to work with regular geometry or regular particles exported from Houdini as alembic to vray.

Is this a known problem or am I missing something?


Cheers,
Simon

[ivaylo.ivanov]

You are using V-Ray 3.0 and the motion vector color set, right? Sadly, there are no errors if something goes wrong with this set, and V-Ray continues trying other possible names for the velocity. Is it possible to send the abc file and the set name to the support?

[simon.ekeberg]

I'm using a vray proxy node to bring in the alembic, and my alembic attribute for velocity is called "v" (it's not a color type vector, but a regular float vector).

Hmm, on closer inspection, I don'tn think Houdini is writing the velocity attribute for the instances. I will investigate further!

[ivaylo.ivanov]

"v", "velocities", "velocity" should work automatically. Otherwise, you can specify custom name in motion vector color set of the proxy.