Vray Volume Grid update issues....

[MutantPixel]

I'm playing a lot with the Vray volume grid item, bringing in simulations from Embergen, but I'm having all kinds of issues. If I update the Input Cache file, I have to change the render engine from CPU to GPU to get it to 'see' the new caches. If I restart, it seems to use the old cache. Also, if I make a change to any setting, such as change the fire color gradient, it forces a preview update, but it doesn't actually update with the new setting. I have to press 'Restart RT' and go through the whole update process again to actually see any setting changes for the Volume item with a VDB. I also thought there were problems with scaling VDB files, but it turns out that once in a while, for some reason changing certain settings, makes the render turn solid white. On a simple scene I can 'fix' it by changing render engine and then back again. But in my actual scene, it is far too large for GPU rendering and no amount of restarting RT seems to fix the problem. Images attached.

[vladimir.nedev]

If I update the Input Cache file, I have to change the render engine from CPU to GPU to get it to 'see' the new caches. If I restart, it seems to use the old cache.

Do you mean changing the contents of the cache, but leaving the file name the same ?
It should be enough to just restart RT, or stop and then start it again.

I am not familiar with what happens internally in the volume grid code, but I highly doubt that changing the engine between CPU and GPU helps.

You could also save new versions as differently named files and select the new file. This seems to get updated properly.

Also, if I make a change to any setting, such as change the fire color gradient, it forces a preview update, but it doesn't actually update with the new setting. I have to press 'Restart RT' and go through the whole update process again to actually see any setting changes for the Volume item with a VDB.

Is that with the GPU engine ? With the CPU engine, the color gradient seems to be updating properly.

Try disabling the light cache on the volume grid (see attached screen-shot).
This should help with the updates.

I also thought there were problems with scaling VDB files, but it turns out that once in a while, for some reason changing certain settings, makes the render turn solid white.

What if you restart Modo completely. Does it gets fixed then ?
We would need the vdb file and some sort of steps to reproduce this.

Greetings,
Vladimir Nedev

[vladimir.nedev]

The light cache option to disable.

[MutantPixel]

Thank you so much again for the help Vladimir, but it's still no go. No matter what change I make to the Volume Grid item, the RT preview window will trigger a redraw, but it doesn't actually reflect that change until I hit 'Restart RT" on either CPU of GPU renderer. CPU was a little too slow for this video though. Here is a quick video of my process and settings--

https://www.dropbox.com/s/20pfcw93fq...nTest.mp4?dl=0

I've tried maybe 4 or 5 separate VDB output files from a couple different versions of Embergen. I'm still investigating what causes the volume to go solid white though and hope to find you a solid set of repeatable steps for that when I have the opportunity.

[boyan]

Hey, James,

Thank you for the post. Could you please, disable the LC option located into the volume grid menu, for more info please check Vladimir's post /image/ above. Please note, that some of the volume grid features are not implemented to work (Light Cache and Light from Fire options) with GPU .
This might be the reason to get those behaviors.
Cheers,

[MutantPixel]

I've been in contact with the developers over at JangaFX and they are aware that there is something currently 'off'' with their VDB exports. I did some testing for them in Vray and it appears older VDB files work fine. So for now it seems likely it is not a Vray problem at all. They are aware of the issue and are looking in to it. I'll keep you updated if I find anything further.