Renders go slower and slower. Why?
sarge74
Posts: 121
Ok, so I've posted about this before and taken part in some discussions about it, but never quite get an anwer. So I'm rendering scenes for a comic book. Rendering in Iray, default settings with a 1500x1200 images size. Scene consists of two G3's, their clothing and a simple room. Usually using an HDRI lighting, sometimes an emissive plane. I render my first comic book panel. Tongiht when I started it took 14 minutes. So I'm off and working. Then at about the fifth render things start slowing. By render six, the same scene is taking over 40 minutes. Sometimes saving and shutting down Daz will fix this, but when I do, I don't get back to 14 mintues. Its the exact same scene, lights, figures, cameras, everyting. I've installed GPU-Z as suggested to monitor GPU memory and temps. Memeory seems to be fine. Maybe "memory used" will be at 300MB or so inbetween renders and temp might get up to 60 degrees C, but not over. I'm using the latest install of DAZ, Windows 10, a NVIDIA 1060 with 3GB.
Any one know why this keeps happening? Its driving me nuts!
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Comments
You need to look at the GPU load to determine if the card is still being used for renders. If you see that percentage drop back down, Iray took the card out of the render queue and you're running on CPU only.
"Memory Used" of just 300 megabytes is way too low for the scene you are describing. That's about the amount you need as overhead for displaying on the monitor at 2K resolution.
I wasn't clear enough. In between renders its around 300, so I know its clearing and not the cause of my gradual slow down. Durring the render, its like 2,800 or more. Roughly. Its load is at 99% usually and on my task manager, Daz is using about 50% of CPU. Those numbers don't seem to change.
Just trying to find some answers and maybe... maybe a solution to this annoying slow down that's killing my work flow.
Any help?
So tonight, rendered the same scene I've been working with. Two g3's, a simple room, two emisive planes for lighting. First render took 22 minutes. Fifth render took nearly two hours. Sames exact scene, just a slightly different camera angle and poses. There's something going wrong here! I've attached my GPUZ sreen shot for the first.
Here's the fifth render GPUZ screen shot.
You need to reduce your texture sizes. The scene is taking up too much of your card's 3GB, and it's getting moved to the CPU. The memory holds geometry besides textures, along with the computations that Iray is performing (and I think the image, too, until it's saved), and if you're using the card for your monitor, there's a hit for that, too, and don't forget Windows 10 holds some if you are using it as the monitor card. But almost all DAZ Content has large textures. Get the new scene optimizer in the store. Works great from reports so far, and is a lot cheaper than buying a card with more memory. Here's the thread https://www.daz3d.com/forums/discussion/164851/just-released-scene-optimizer-commercial/p1
most of the render time is based in your graphics card
quadro cards are designed for rendering...everything else is not
this is the cheapest one I seen on amazon, always check your computer specs before
investing in hardware
NVIDIA Quadro K420 Graphics Card - Low Profile Graphic Cards 4X60K59925
then... things like textures and such modifiy the render time
your graphics card dictates the base time that gets modified.
this is just from personal experience
peace
Evidently no one is looking at the OPs screenshots. In both cases (first and fifth renders) the GPU is running at considerable usage, so I doubt it's dropping to CPU. We would need to see the log file at the start of each render to be sure though.
Also, changing the camera (even slightly) can result in significant changes to the render complexity. But if nothing is changing between renders, something else is causing the slowdown. Check system memory usage.....if DS is using up too much system RAM, it may be going to swap file, which can slow things down to a crawl, even with Iray running on the GPU (those results updates have to stream through and be saved to disk.)
Are the screen shots during a successful render, or when it's slowed down. You're right at 3G, so a small hiccup will toss the render out to the CPU.
Try unticking the CPU from the render queue, so that it will not be used as a fallback. If your renders are getting kicked out of the card, it will be obvious.
Render > Advanced settings tab > uncheck OptiX.
When you're right on the border of VRAM limits, subsequent renders can be much slower. Unchecking OptiX has been known to resolve the issue.
Thank you, Kevin. That seems logical. So would the huge texture files slow renders down more and more each time? What is backing up that makes the render times slow like that?
Thanks for the input, everyone. The screen shots were durring render, about 5-10 minutes in for each. I didn't get kicked to CPU at all. and my Tack Manager lists DAZ as using about 50% of my CPU RAM durring render. The GPU render just progressively gets slower and slower.
Any further input or thoughts are appreciated as I try to solve this puzzle. Thanks
Are you rendering to a file? If so, that should clear the memory when it's done each time. Try it if you haven't.
Yes. Rendering to file. Thanks.
Any suggestions, anyone?
Not really a solution but I would never get to 5 renders while in the same scene. I would exit DS and restart after 3, max. I've even seen significant render time improvements after a reboot. I'm convinced that something is wrong with IRay and VRAM but it is difficult to tie-down. As someone said above, even moving a light can have a drastic effect.
An exception is obviously when rendering animations. I render to an image series and obviously I need to stay in the scene for the whole process. However, as Kevin said, they are rendered to file so perhaps that accounts for the consistency there. Just a point of caution though: if I am close to the VRAM limit then it will render the first one or two then drop to CPU. I've started using the Scene Optimiser product recently and that helps a lot.
Thank you, Marble. It is reassuring to finally hear others are having the some issue with multiple renders. I used to render all night over and over with 3Delight and ol' V4/M4. I miss those productive comic book making days. Iray and G3 are just too awesome now to go back, I just wish I could get back into that work groove again with out all this slowing down and the saving/restarting cuz something has bogged down the system. I might try the render to file thing. Not sure what that is or what I'm doing, but I plan to find out.
I think the issue is that rendering to the Render Pane keeps the Iray Context alive....if the render could be continued (or render settings tweaked and continued), it stays. Closing a pane in DS doesn't really 'close' the pane....it just hides it, typically. DS may be keeping the render pane around even after we click 'close', 'cancel', or the 'X'....It may not keep everything, and of course, the data would stay loaded.....but it would explain why rendering to file doesn't seem to suffer from the same problem.
I think you may be correct - I've noticed that in GPU-Z. Render to the pane and cancel/close. The VRAM number drops but not to the the pre-render amount. Start again and the total may be higher than the first render. I've also noticed that there is often a spike in the VRAM number which happens at the point when those VERBOSE messages appear in the activity window. If the scene is close to the limit, that spike is sometimes enough to drop it to CPU.
H phoenix, Marble, this may be the first time I've actually heard a reason that makes sense for the slow down I'm experiencing. Thank you!