Vray 2.0: Excessive RAM usage

[BBB3]

Vlado,
Forgive me for raising something that was discussed in a different post but I figured it had a better chance to catch your eye by making it a separate thread here.
Several of us have noticed a relatively considerable increase in ram usage from 1.5 to 2.0 on the same scenes.
Can you tell us a little about what causes it? Is this to do with how 2.0 handles geometry? Or bitmaps? Or displacement? Or is it to do with the size of the output?
Is there any approach one should take to mimise the difference?
Any input much appreciated as I'm hitting the ram ceiling on a project I'm working on right now.

[PIXELBOX_SRO]

since crossing to vray 2.0, i ve been hitting the 16GB RAM limit very often too

[vlado]

If you have not updated to V-Ray 2.1, it would be best to do that - it fixes one particular issue in that regard.

In any case, V-Ray 2.x may take somewhat more RAM than V-Ray 1.5 when using dynamic geometry (proxies, displacement etc). This was done to avoid a particular issue - if you remember, there was a problem where a scene with lots of dynamic geometry rendered slower when using a saved irradiance map than the same scene rendered with a new irradiance map from scratch (although the same slowdown could happen in other circumstances as well, depending on how the rays hit the geometry). While the fix solved the difference in render times and improved multithreading a lot, it also caused V-Ray to cache geometry more aggressively, which is what causes the increased memory usage. In many cases eventually the same amount of RAM was allocated by V-Ray 1.5 too, but it took a longer time.

We are of course looking at ways to improve the RAM usage while keeping the performance, but for the moment this is the situation. I was also thinking of adding an environment variable to switch to the previous behavior, so if you are interested in this, let me know and I'll see what can be done.

Best regards,
Vlado

[PIXELBOX_SRO]

thanks for the explanation Vlado

[Visual3D]

I think an environment variable would be great. In that way whenever I'm not using a saved irradiance map I'd change to the old way, as memory usage is reaching the limit in a lot of scenes I had no problems before too.

[BBB3]

I'm with Visual3D on this. An environment variable would be useful in those borderline cases where we are reaching the limit and things start caching to disk...

[PIXELBOX_SRO]

+1..i forgot to mention that in my previous post

[peterguthrie]

+1 from me too

[BBB3]

Yes, it definitely seem that the price to pay across the board (pretty drastic limits on the size of scenes) for an improvement in a relatively specific situation (faster renders when using saved IM with lots of dynamic geometry) is too high. For me one huge benefit of Vray compared to other renderers has been the ability to render very large scenes. This is an advantage that is being eroded in exchange for an (at least to me) relatively insignificant benefit.

[PIXELBOX_SRO]

thats spot on Bertrand

[vlado]

Yes, it definitely seem that the price to pay across the board (pretty drastic limits on the size of scenes) for an improvement in a relatively specific situation (faster renders when using saved IM with lots of dynamic geometry) is too high. For me one huge benefit of Vray compared to other renderers has been the ability to render very large scenes. This is an advantage that is being eroded in exchange for an (at least to me) relatively insignificant benefit.

This is not quite correct; the irradiance map issue is just one instance where the particular underlying problem is apparent; the issue also happened in other situations, and could slow down the rendering significantly even in cases where there is enough available RAM.

Best regards,
Vlado

[BBB3]

I see. Still, in an ideal world, it would nice to have at least the option of choosing between ram efficiency and performance depending on the scene. Whenever the available ram is exceeded, better performance is moot anyway. That's unless it's particularly difficult or tricky to do for some reason.

[vlado]

Well, this is why I suggested the environment variable...

Best regards,
Vlado

[3DMK]

Sorry to invade the post, but What are you guys doing to max out 16GB of RAM???? That's a hell of a LOT of geometry to fill up 16gb....lol
I guess I have always been paranoid about running out of RAM so I PROXY almost everything that's duplicated & hardly ever go over 4-6GB with massive scenes including 3D trees everywhere. Takes longer to setup but worth it IMO, as you can avoid this issue altogether. I find it also important to try not to use Displacement as this seems to fill up the RAM real quick.

Cheers
Jamie

[vlado]

Well, one particular example scene that we got had a lot of 3d displacement, which produced several billion unique triangles....

Best regards,
Vlado