Instanced openVDB clouds

[colorbleed]

We're working on a new film taking place in the air, and we'll be doing a lot of cloud shots. Now we're looking to create big cloudscapes using VDB and get good fluffy (and hopefully fast!) renders out with V-Ray. We're hitting some harder spots on getting the scenes set up quickly.

We're working on V-Ray 3.6001 and Maya 2018.1

1. It doesn't seem to work to instance (MASH or other particle instancer methods) the VRayVolumeGrid.
Are there any workarounds for this? Or should we stick with just copies and instances regularly in the scene?

2. When instancing the VDB clouds many times the viewport gets really slow, even when visibilities are set to bounding boxes.
The only workaround we've found so far is to disable the viewport display of the grids completely, and instead parent a cube polygon mesh shape underneath the grid's transform that matches the grid's bounding box. Then we use that "mesh cube" as preview in the viewport. Any other solutions or are we missing a particular setting?

3. Any other pointers on rendering large cloudscapes? What workflows would be recommended?
We'd be happy to investigate!

[shaio]

Hi,
for N.1 currently we don't support instancing of VolumeGrids so I'll write a feature request about this.
for N.2 please try using the "Detail reduction" option under the Preview rollout in the VolumeGrid node. Set it to a suitable value (maybe something above 10 or 15) and then make the instances. This should significantly improve the viewport performance.
for N.3 I'look for some usful information and will share it with you.

[colorbleed]

for N.1 currently we don't support instancing volumegrids so I'll write a feature request about this.

Thanks.

for N.2 please try using the "Detail reduction" option under the Preview rollout in the VolumeGrid node. Set it to a suitable value (maybe something above 10 or 15) and then make the instances. This should significantly improve the viewport performance.

Unfortunately this is not giving us the speed we're looking for. It remains really slow with over 15 volume grids. Even setting the drawing overrides of the shapes to bounding box or disabling the "preview" in the volume grid pretty much completely makes just moving the camera around very slow. Our only workaround up to this point that worked was to actually hide the VRayVolumeGrid shapes completely (disabling the visibility)

for N.3 I'look for some usful information and will share it with you.

Great! One of our challenges is to also render a massive Cumulonimbus cloud. Exciting project, just so many clouds. Any tips are greatly appreciated!

[shaio]

Unfortunately this is the limit of the optimisations that we have for the viewport previews. We'll be working on improving this and it's in our to do list, but it isn't planned for any time soon.

[colorbleed]

Unfortunately this is the limit of the optimisations that we have for the viewport previews. We'll be working on improving this and it's in our to do list, but it isn't planned for any time soon.

No problem, for now we'll just disable the LOD visibility of the volume grids.

Did you have any other points for doing wide very deep cloud landscapes in an optimal fashion?

For example we've tried a scene with 1700 times the same VDB cloud instanced across the scene, but this is very unoptimized wheras other renderers seem to instantly be able to render this.

[shaio]

Great! One of our challenges is to also render a massive Cumulonimbus cloud. Exciting project, just so many clouds. Any tips are greatly appreciated!

Here are some tips that should help you optimize the rendering times:

• Make sure to play with the Step Size (%) and the Shadow Step size which will help you speed up the rendering for the cost of some quality (more noisy image)
• The main slowdowns while rendering the clouds would be places where you have multiple clouds behind the one that is currently rendering. Such areas are more slowly for rendering because of the opacity. Setting opacity modes under the Smoke opacity rolloud could help improving the performance in such areas
• If you use Light Cache in the Smoke rollout, You could use the Light Cache Speedup to improve the performance for the cost of some quality again

Sometimes finding a good balance with those parameters helps a lot.

[colorbleed]

At this point the rendertimes don't seem to be the biggest issue, instead it's that with 1000s of VRayVolumeGrid the (prior to rendering) optimization takes a very long time (even if it's the same VDB file).

[squintnic]

we wrote a simple mass change volume grid scripts to get around this.

[shaio]

At this point the rendertimes don't seem to be the biggest issue, instead it's that with 1000s of VRayVolumeGrid the (prior to rendering) optimization takes a very long time (even if it's the same VDB file).

This kind of prerender optimizations are also in our to do list since other users also requested thе issue. Sorry for the inconvenience

[smbell]

we wrote a simple mass change volume grid scripts to get around this.

I'm about to have to do a similar shot with tons of vdb clouds. Can you talk about the script and what exactly it did?

[smbell]

Any update on this?

I'm currently working on a clouds shot with lots of openVDB clouds and I'm having some major problems. I tried instancing them, even though it's not supported, it did render with a handful of clouds, but when I got around 20 clouds the memory just filled up until it paged out and I had to kill the render. I duplicated them instead of instanced and the memory usage still hit the roof after only 20 or so clouds being loaded. Only when I turned off the light cache optimization was the memory use normal and I could render, except now it's taking ages and ages to render. Is tons of memory usage with the light cache optimization a normal occurrence? I'm going to need hundreds more clouds and was hoping to benefit from the speed increase.

[shaio]

Hi,
unfortunately yes the memory usage may vary based on the number of copies and the light cache. We are working on optimizing these kind of cases and the support of the instancer is also in our to do list. I'll keep the thread updated when we have some improvements or workaround regarding these issues.

[smbell]

I see, thanks for the info!

[fasterG]

Hi,
Is there a way to use VolumeGrid VDB clouds in MASH?
I just watched a Redshift tutorial where he exported the original cloud as a proxy and was then able to scatter the proxy around using MASH. Is there a similar way in VRay (Next)?
Thanx!

[shaio]

Hi,
sorry for the delayed answer. You should be able to instance VolumeGrid with any kind of cache with V-Ray Next and MASH. The only step needed is to set the Render Mode to Volumetric Geometry in the VolumeGrid Rendering rollout. Let me know if you have any issues.