[HOU-3578] Volume Grid Rendering Speed in H19.5 Compared to Maya 2023 and VRay 6

V-Ray V-Ray for Houdini General
1

I have a VDB sequence of a fire simulation, which takes around 1min in Maya to render and over 3min in Houdini. I double checked all settings and I am using the same camera and light setup.
Is there any obvious reason for this? Is the jump from vray5 to 6 accelerating this much? Never had the feeling before in Maya from 5 to 6.

I am rendering in LOPS through Husk.

2

I figured out what caused the speed differences. It was because I exported from Maya Bifrost Aero to Houdini, and the change in scale. I had to compensate the scaling in the Volume Grid Shader Step % and Shadow Step %
This way the noise threshold and rendertimes act normal again.

The question is, thy the settings have to be adjusted anyway?

3

So this is weird. If I export a Houdini Pyro Sim to VDB and scale it up in Maya to match Houdini scale, it renders blazing fast in Maya. But over in Houdini the rendertimes are huge argain. Same light setup and rendersettings applied. Vray 6, latest Maya 2023.3, latest Houdini 19.5.435.

Please help me on what I am missing here.

4

I found that in houdini vray volume rendering was always weirdly slow. I couldn’t compare that to maya until recently (because we had no current vray maya lics). But now I can and I have to say the difference in general renderspeed and snappiness of ipr when using volumes in maya is so much better than in houdiini vray that there must be something not right there. This really needs to be looked into.

5

Cool that you guys brought this up, I noticed some render time discrepancy between rendering inside Houdini vs rendering in the farm (V-Ray standalone).

Here’s the same frame rendered locally and in the farm, same exact everything, and the farm render uses the same hardware specification as the workstation I rendered the local version.

Local render: 7m 48s

volumes_local.jpg
volumes_local.jpg1089×459 66.6 KB

Farm render: 2m 50s
volumes_farm.jpg

This should definitly be looked at @Gosho.Genchev

Best,
David.
volumes_farm.jpg

6

hey guys!

I found out, that when I disable Probabilistic Volumes in Maya I get the same speed and behaviour as in Houdini, which suggests that something in Houdini is wrong. Please see this thread:
https://forums.chaos.com/forum/v-ray-for-houdini-forums/v-ray-for-houdini-problems/1167662-adaptive-bucket-splitting-broken

Hope we can sort this out soon.

7

It would appear both you and @doppelgaengerdigital are right - the export is correct so running the VRScene through Standalone would give you much faster render times. For some reason the probabilistic option is not used for the GUI/VFB rendering inside of Houdini.

I’m logging it now and we’ll fix this ASAP.

Best regards!