Rt ram usage vray 3.01.10

V-Ray GPU V-Ray GPU :: Issues
1

just doing a quick but heavy test of RT GPU and forestpack.

wanted to see how much i could cram into my 4gb gpu.

its a 25 sq km bumpy plane with a forest object referencing 6 instanced proxy trees, with a fairly dense scatter.

in normal vray, it uses 6gb in total when rendering.. this includes max and viewports etc. using progressive sampler ( all at defaults in vray actually)

so in theory shouldnt be far off fitting in the gpu ram.

However, when i switch over to rt gpu, it gets to the “compiling geometry” stage, in the vray rt floater, and my ram usage just goes up and up.. currently at 26gb and still slowly climbing. (after about 5-10 mins of waiting)

vray rt hasnt even started doing anything yet, and my gpu is only using the 1gb it was before i started.

is this expected..? bit odd that rt gpu should need so much system ram to deal with a file that renders without stressing my system at all normally.

-update, my ram is now maxed out at 32 gb and still nothing has happened. i guess ill be cancelling.

edit:
i cut the forestpack back to a smattering of trees, and now it “only” hits 10.5 gb of ram usage before sorting itself out and starting the render.

update: rt cpu behaves properly, uses only 6gb when rendering.

2

This is strange; do you think you can get me the scene to vlado@chaosgroup.com ?

Best regards,
Vlado

3

sure can.. ill send it later this eve..

4

ive sent you the file via wetransfer

5

in case it matters, im using max 2014 x64, and forest pro 4.3.4

6

I’ve reproduced the problem, thanks.

7

just wanted to note that this problem still persists with vray 3.20.02

8

That’s correct, the issue hasn’t been solved yet.
We’ll let you know when it is.

9

could somebody clarify what the problem is? i.e. forestpack is broken with RT gpu? or just specific features/usage scenarios i should avoid..

10

I don’t know what the problem is yet. One of the developers is looking into it.

Best regards,
Vlado

11

I have been having the same problem in some scenes (without using forest pack). It is a fairly large scene and should be rendered on 4000*2828. Translation seems to stop after building global light manager, follow diagnostic massages only arrive after a long time (even though they do have a timestamp indicating they happened only seconds after previous opperations). Vray RT rendering (GPU) then starts but finishes after just ~4 seconds, no warnings or problems noted in the diag screen. The Max/Vray render progress bar panel keeps showing it is rendering without anything actually happening. I noticed the problem started when I reached 90+% of my ram (16GB). Rendering on quarter resolution seems to work properly. Very curious if this is a software issue or I should just expand my RAM. ps, Scene is rendered on a Titan X and GPUz states it’s max VRAM use was 5gb while then Vray RT diag screen reports a usage of 8GB.

12

You can put more ram or just for a quick test try disabling windows paging and render, in that case 3ds max should crash (if the problem is insufficient ram).

13

Would there be a way to know how much ram would actually be needed for this translation phase? As I probably could get an upgrade for my workstation, it would be less than fun if the problem persists with double the ram. Or is this ram consumption impossible to predict?

14

I think we fixed some issues related to this recently. Would it be possible to send a scene for testing?

Best regards,
Vlado

15

I’m afraid the scenes in which I experienced this problem included alot of assets which I can’t share. The scenes did include large numbers of instanced objects, proxies (trees) and was supposed to be rendered at high resolution (4500*3000). I don’t have time to create a completely new scene to replicate the problem at the moment. If needed I’ll try to throw something together in more quite hours.

ps. Attached a picture to the wrong post, nevermind the image, maybe a mod can remove it?

opencl devices 2.png
opencl devices 2.png794×959 40.4 KB

16

Playing around some more with the scene I noticed the ram problem emerges with translating displacement. Once it reaches this point the ram fills up in a constant steady pace until it’s full, from that point on the system crawls until it decides it is finished after some hours (even when the goals set in the render settings are not reached.) The proxies in the scene did not influence the problem noticably. I’m suprised the ram usage is so high during translation despite it fitting on the Vram with ease. Is this a potential issue or simply a technical limitation at this time?

17

i believe its due to the how displacement is handled in RT.. when you render displacement on gpu, it is first created as a complete mesh on the cpu, before being uploaded onto the gpu for rendering. with really heavy displaced scened this can take much more ram that the final outputted mesh does.. or something like that.

one thing ive found tht helps is to subdivide your base mesh as finely as possible before rendering. this seems to give less work for the “precalculation” of the displacement on the cpu.

18

You can also increase the “edge length” for the displacement, especially if you render large resolutions.

Best regards,
Vlado

19

just to revive the original theme of this thread.. same test scene i used then, basic landscape with a modest forest of proxies generated by forestpack..

with 3.02.03 i still have the issue whre the scene renders on cpu with 6gb ram, but on gpu it maxes out my ram on the compiling geometry stage, and seems it will never start rendering.

i thought id try converting the forest to plain instanced proxies..

this at least works better than forestpack, but a) it still uses 17gb of ram compiling geometry ( as opposed to maximum 6gb when using cpu) and also, after getting to the actual render, within a few seconds i get a “cuda error code 719: exception occurred on the device while executing a kernel”, and it stops rendering. ram usage on gpu at time of crash was 4.6gb.

not looking too hot for my masterplan stuff on gpu at the moment :frowning:

i can send an updated scene if it would help.

20

ok ive managed to get it to render by reducing the number of trees from 40,000 to 30,000.. odd id have assumed it would not be limited unless the ram was full. could it have been some coplanar faces amongs the intersecting trees? id not imagine that would throw an error either.

anyway next problem:

i got a decent render out in about 10 minutes, so i thought id try a few frames overnight to see how the gpu behaves, and check the shimmering in the foliage.

i set 200 frames going, first frame completed ok, using about 4gb on gpu and vray.exe using about 7gb
it saved the frame, moved onto frame 2 and…stopped. before the gpu even got involved.

ram usage rose again on vray rt up to about 12gb, then stopped rising… i waited 15 minutes then cancelled.

max is half crashed (i cant close render dialog, which wont cancel, but i can save the file and spin the viewport.)

any ideas? so far everythng im trying on rt beyond the benchmark scene seems to have issues :frowning:

-ive wetransferred latest scene to vlado.

-update:

with 95% tree reduction, the scene renders as expected.. 50% reduction it still locks after first frame.

-2nd update:

with 85% reduction in trees i can see perhaps the “crash” may just be an extremely long pause.. with 85% reduction, i wait about a minute for the next frame to start, but it does start.

HOWEVER, i can see even after the 3rd frame, that the ram is not being cleared after each frame. each frame adds a gb to the ram usage on the host pc. not good! at that rate id only be able to render about 28 frames before my ram maxes out.

considering with 20k trees, it added 6gb before starting the second frame, id only be able to render a handful of frames before game over. assuming i could be bothered to actually wait for the 15+minutes to see if it actually starts the next frame at all.

3rd update:

opencl has same issue as cuda. i let it do 9 frames and my ram usage climbed from 7gb to 12.3 over the course of those frames.

4th update:

even with only *ONE* proxy tree in the scene, i -still- get the ram climbing after each frame. obviously only by a smaller amount, but after 50 frames, its gone up a few GB.

5th update: at least on the ram increase between frames, it seems to be related to the tree material. if i put a flat grey vraymtl on the trees, the ram usage stays constant. i tried just removing the 2sided from the leaves, but still had the issue.. i also found a “forest colour” map in the leaf diffuse, but removing that didnt help either.