[HOU-2437] Vrscene scene - Slow export with VDBs

[david.anastacio]

Hi,

Were running into another situation here with the vrscene exports, when using volumes (VDBs) the exports are taking quite a bit of time (some scenes taking hours).
The "file" nodes used are set to load as "Packed Disk Primitives" and display as "Bounding Box", and the VDB caches are big in some scenes, and other scenes have several caches loaded. The resulting vrscenes are small, just megabytes as expected since everything is set to Packed Primitives, but they are taking like 20-30 seconds per frame, and over 200-300 frames that leads to 1-2 hours.

I prepared a small test scene that is not as problematic but shows the issue a bit. Just 2 simple vdbs loaded and 20 frames take 1 minute to export and the resulting vrscene is 108kb. Why is it taking so long since it's not writting any data?

Another phenomenon is the increase of RAM when generating the vrscenes, the more caches and the bigger the caches the higher the ram goes. In this example Houdini goes from 400Mb of ram to 4Gb just exporting the vrcene.
Before vrscene start:

After/during vrscene creation:

In theory this should just be vray writting a vdb path to the vrscene, what's happening that causes the ram to go up and to take so long per frame? And is there anything that can be done to improve this?

Best,
David.

[glacierise]

Funny you say that - we've just reported that too. Takes more ram and time than it should, and it's failing if you load up too many/heavy volumes, seems like it does actually load them up in memory. Would be great to have that fixed.

[david.anastacio]

Hi, bringing back this one.

This issue is still happening both in V-Ray 4.3 and 5. Is there anything being done about it?

Just trying a volume in V-Ray 5 and it's taking like an hour to generate a vrscene with 110 frames and a single vdb volume in it (set to packed disk primitive), and the resulting vrscene file is just 300kb.

Best,
David.

[Dubbie99]

Also seeing this issue. It’s baffling to me why exports in general take so long.

[david.anastacio]

hi again,

Gosho.Genchev, any update on this topic?

Back in February when we had our meeting it sounded like this was close to be done, but we had no update on this for a while.

Also liked to this other post: https://forums.chaosgroup.com/forum/...80#post1101480

Best,
David.

[glacierise]

From what I understand so far, it's because the bounding box of the vdb needs to be created - interesting if there are ways to do this faster

[david.anastacio]

From what I understand so far, it's because the bounding box of the vdb needs to be created - interesting if there are ways to do this faster

It could be that I might have understand it wrong from the meeting we had with Gosho, but it sounded like like they were reading the bounding box but they didn't even needed to do that.

Best,
David.

[glacierise]

Cool that's interesting, and sounds like an easier fix. But I guess some type of bounding box is necessary with the packed disk primitives, to figure out when to start loading it up in memory?