Hi,

I'm trying to render some motion vectors from a Pyro fluid to use to blend between sprite frames for game FX. The technique I'm trying to work with is described here: http://www.klemenlozar.com/frame-blending-with-motion-vectors/ [klemenlozar.com]

I want something like this:
http://imgur.com/a/JaTDZ [imgur.com]


I've created a Pyro sim and have tried rendering out motion vectors using the RSMB_MV shader applied to my Pyro. This just renders out a blank colour, with no vector information applied.

I'm pretty new to Houdini and I don't know if this is the right technique, or is there another way?

what about converting the vdb to geometry and then transfer the V attribute to the mesh, now the mesh should be able to render the V. I guess.

For one, you need to add the extra image plane on the Mantra rop so that it knows to render it, in your case the name would be motion_vector, and set the type to vector.

As well, you can get the world P just by clicking it on on the rop and do not need extra nodes in your shader for that. There have been a few changes lately to how houdini handles extra image planes, with the newer versions allowing for the standard channels to be activated through click on via toggles on the Mantra Rop(Diffuse, specular, reflection, P, Z Normal, etc…

Did you get anywhere with this? I'm trying to do the same thing.
Another approach I tried was to use the velocity field as the density color but it didn't give me the result I wanted either.