Falling back to CPU on simple scenes

michaelpomar

I'm getting so very tired of this issue. I have this one EXTREMELY simple indoor scene, with one Genesis 9 char in a simple dress hair and heels, some make up and nothing else, she's in a bedroom with only one wall visible and tow side walls, ceiling and a floor enabled to ensure the light doesn't stream through from the HDRI. The HDRI I change from an 8k, I've used in other scenes with ZERO problem to the lowest res one I could find on my system. I put a simple three point lighting system in with a point light too to light up her face. 

I'm using a i6700k with a RTX2070Super (8GB) to render.

I have tried to render the same scene all day today, about 10 times hiding stuff using opmitizer tools also but with always the same result, after 400 or so iteration falls back to CPU. Watching Task Manager religiously CUDA is around 98-100% used during the point it's using the GPU, memory though seems to be stuck around 6GB of the 8GB. Initially thought this was a problem with my video card but noticed similar behaviour on another computer I have running a animation on (that's taking all bloody day for a 3 second animation in the same ever so simple scene), that one hasn't droped to CPU though and it's running on a GTX1070.

So I'm not thinking it's a hardware issue, I am thinking there is something in the scene though that could be causing it, but I have used the bedroom scene in other scenes and this character in this and other scenes without seeing this issue consistently pop up. A restart fixes the fall back to CPU problem all the time but not with this particular scene, I've even tried full restarting of my system, running nothing other than Daz on the rig, everything and before anyone suggests it, yes I'm on the latest Nvidia drivers.

michaelpomar

Think I have worked out the issue and it's a lesson learned for me at least. Looking deeper into the troubleshooting log, I noticed a lot of illegal memory access erors but hidden at the top of the list was a different error that pointed me to the culprit. A message talking about material surces, initially I suspected that I had mistakingly increased the subD level of the character, but it wasn't that. I had applied a shader preset to the dress she was wearing, I removed the dress all together, re-dressed her in the same dress and did not apply the shader, now CUDA is at 100% still through 894 iterations at 95% convergence :) Lesson learned = don't use that shader ! Which is a shame because I liked the coral colour and now I need to redo a couple of scenes and stop my animation and restart it again because her dress is in a different colour :( 

michaelpomar

Spoke too soon fell back to CPU at 98%, more troubleshooting ahead of me :( This is not fun DAZ !!

TimberWolf

The Windows task manager is not the ideal tool to monitor GPU memory useage. If you don't have it, download the GPU-Z utility and have that running whilst your scene renders, monitoring the VRAM useage of your card. You already know what the issue is - you've blown through your available VRAM - and with only 8GB it's quite easy to do these days, especially with the memory hungry G9 models but I can't recall a situation where a render completed to 98% and *then* dropped to CPU.

The only scenario I can imagine is that you started something else which upped the VRAM useage (e.g., watched a video, opened a number of browser tabs) but I very much doubt you did this and I'm also assuming that the 2070 is your only card in this case. I very much doubt you have a hardware problem either.

GPU-Z: https://www.techpowerup.com/download/techpowerup-gpu-z/

As a quick suggestion, try changing the thresholds at which Daz applies texture compression in Render Settings -> Advanced (tab) -> Texture Compression. Drop the Medium Threshold to 256 and the High Threshold to 512. See if that helps. If it works, start doubling those numbers until it doesn't. 512/1024, 1024/2048 etc. If that doesn't work you may have to start reducing the texture sizes of some elements of your scene and there is a utility available in the store to help with that. Try the simple stuff first...

Personally I would consider a 12GB GPU to be entry level for G9. It's not that you can't use an 8GB card - you can - but you're going to be sailing close to the wind every time without a large amount of optimisation.

michaelpomar

Thanks for that TimberWolf I woill look into the texture compressions. 

In terms of G9, there was a need for that for my project I'm working on, I was initially going to go with G8 but on advice of a few others I switched to G9. I've not encountered however too many performance issues that I could resolve with a simple restart of Daz and/or some optimization until this one particular scene which has been stubborn, I think I have got over the immediate issues however, something with my 3 point lighting setup I believe was causing it as I started the scene a fresh but just used HDRI for lighting only and no CPU fall backs in 3 shots I have taken thus far.

I know my rig is under powered, I made the mistake of switching to team red and a 6750XT for my main system a few years back, before I started with Daz. Would love to be able to use the power of that card in these renders but alas I doubt that will ever be possible :( Like I said though the majority of time I'm able to work around the limitations by messsing around with camera angles and hide elements of the scene, along with the optimizers out there.