Render Elements RAM usage

[tetsuo]

Hi,

I soon as I put some render elements, RAM goes crazy and crash.
Even with only ZDepth, it goes to the top (64go)...

And clicking cancel before it crashs takes age to unload memory.

I'm on version 3.12.01 Nightly, Build ID: 2019031428995, with VRay Next 1.1

Please help,
thanks.

[tetsuo]

Seems to happen when not using smoke light cache.

[tetsuo]

After some more tests, the RAM raises as long as the render lasts with this combination :
- Smoke "Ray-Traced (GI only)" mode
- Smoke "Light cache" disabled
- GI enabled

I am not using one of the approximation modes becauses they're not compatible with "Volumetric Geometry", wich I need for render elements rendering.

[tetsuo]

Just rolled back to V-Ray 3, problem disapeared...

Edit : spoke too fast, same issue

[tetsuo]

Here is a scene to play with.

I'm using :
3ds Max 2019.3
Phoenix 3.12.01 Nightly, Build ID: 2019030728978
V-Ray 3.60.05

Try switching render element on and off to see what's happening on RAM, and a never ending render.

Beside the fact that it renders reeeeaaaally slow for what it is, you'll notice that buckets leave artefacts behind them.
Enabling smoke light cache is even worse, no matter Im using BF/BF or BF/LC.

So I wonder, is it possible to render nice, fast, and with render elements ?
This drives me nuts.

Please help.
Thanks.

[Svetlin.Nikolov]

Hey, just reproduced it here using the large smoke preset. Seems to happen in both Volumetric and Volumetric Geometry mode. Turning off all render elements seems to solve it. Looking into it...

[Svetlin.Nikolov]

Alright, should be fixed for tomorrow's nightlies. Thanks a ton for the report!

I couldn't reproduce the artifacts though - please try tomorrow's build and if they are still there, ping me.

As for the render speed, unfortunately for render elements you need to be in volumetric geometry mode, which is slow, and since you want to get scattering, the ray-traced one is slow too. You are also using an intense lighting setup with a dome light and a wide area lights which are not volume friendly at all. A few things that might help - increase the shadow step %, increase the Minimum Visible Opacity - if not to 0.001, then at least to 0.0001. And finally - having enabled 'Use Probabilistic Shading' in the atmosphere settings with GI on means you could adjust the GI samples option in order to speed up rendering - there will be an ideal value for it, which depends a lot on the scene, but too little will be slow, and too much will be slow, so you could trial-end-error a value in the middle.

Finally - using V-Ray Next GPU for getting render elements with this setup would be the fastest possible way - we've been adding render elements support to V-Ray GPU for the last few months, but I am not sure if this is already available in the stable nightlies. If it's not there yet, it will be in the next V-Ray Next update...

Cheers!

[tetsuo]

Thanks a lot Svetlin !

Indeed REs don't show up yet in VRay Next GPU 1.1, but I didn't tried nigthlies, I'll give it a try.

Regarding GPU, I though that it wasn't supporting volumetric geometry mode, cause render was quite the same as volumetric one, and REs was not there.
Really have to dive in it one more time with nigtly. On the other hand it doesn't support grid textures, distance text, etc. So it's a bit prematurate I guess.

You didn't reproduced the bucket artefact with my scene ?
I thought first that it was because of the coarse grid of my test setup.
Maybe it's hardware related ? I use an AMD Ryzen Threadripper 1950X.

Like you said, I'll try a simpler light setup.
However it's amazing how fast it is in approximate mode !

Again, thanks a lot for the great support !

Cheers!

[Svetlin.Nikolov]

Hey,

The great thing about V-Ray GPU from a developer's perspective is that it doesn't have any of that legacy we have for CPU - we can add stuff very easily and don't need to restructure before adding anything new, or keep compatibility with hacks from 10 years ago. So for GPU, the Volumetric Geometry mode won't be needed at all and render elements can be generated with the regular render as it is supposed to be

One important update! Found a render crash in Saturday's Phoenix nightly, and the fix for it will be in tomorrow's Phoenix nightlies, so to be on the safe side, please update again tomorrow.

Cheers!

[tetsuo]

Great !
Thank you Svetlin !