I have a project, that requires me to render out Houdini Pyro simulations in Vray Maya, and the Vray Volumegrid seems like the obvious choice. However, I am getting some very unexpected results from the produced motion blur.
The cache is a .vdb, and all the velocity data is read in correctly by the Vray Volumegrid in the channels menu, and displayed in the preview. I’ve attached photos from the vray render, as well as the Mantra render, to illustrate this (I’m only showing the alpha channel, as it best illustrates the issue I’m having). The Mantra render gives me the correct motion blur, while volumegrid gives me a kind of “ghosting” effect on the motion blur, with some obvious artifacts. It is at if the motion blur only effects a small portion of the smoke.
normally this wouldn’t be a big issue with volumetrics, but these volumes are moving with very high velocities, and needs the motion blur.
The screengrabs are with and without motion blur from each render engine. It should be named accordingly
Hi. I had the same problem with Fire from Houdini rendered in Maya Vray. To get my Vel pass from the VDB I render it using Geometry option. But I quickly realize that it basically converts the whole voxels into geo so your vel pass will not work properly at the comp. So I just did the pass in Houdini scaling my cam and objects accordingly. I think Maya Vray still doesn’t support proper Vel pass render with Vray VDB.
It would be best if you could attach a scene with a volume grid and a single cache.
Which version of V-Ray are you using? Does this still happen if you try the V-Ray Next beta?
Off the top of my head, it’s possible that the velocity y and z channels are swapped, which you could swap manually from the 3rd party channel mapping dialogue, but of course it would be best if this could happen automatically.
Sure, wetransfer works as well. I think we’ve fixed such an issue a few months back, so if the setup works well with V-Ray Next, will make sure to pick the fix to the V-Ray 3.6 stable nightlies so you can get it too.
Here is the download link. Be warned! It is a very ugly sim
I’ve only given you a few frames of cache data. The frame I rendered for the screenshots was frame 1018.
Let me know if you encounter any issues with the files. I prepped this very quickly
Negative, I keep getting interrupted with other tasks. At first sight it seems like you might need an experimental moblur algorithm I have stashed. I will expose it through a script parameter so you can try it out and ping you when it’s in the stable nightlies, hopefully in a couple of days.
Okay, I’m finally on it, I hope tomorrow I will be able to finish the change and merge it into the stable V-Ray 3 nightlies for Maya. Will update you when it’s done.
You are just on time It’s already in the Phoenix and V-Ray Next nightlies and yesterday I backported it to V-Ray 3 for Max and Maya, but the nightly builders have had some issues this morning, so still waiting on the guys to fix them.
If you can tell me which Maya version you are using, I will share you a build in about an hour.
You can enable the algorithm using the ‘mbgrid’ hidden attribute of the VolumeGrid.
It’s already in the Phoenix and V-Ray Next nightlies and yesterday I backported it to V-Ray 3 for Max and Maya, but the nightly builders have had some issues this morning, so still waiting on the guys to fix them.