Help in solving GPU issues when rendering.

[Adrian GT]

I've been using Vray's RTX rendering in 3dsMax lately and been enjoying it so far. These past projects I've been using more complex models and textures for my architectural scenes and I've been getting memory errors when trying to render Full HD scenes.

I can say I'm at an mid-entry level when it comes to computer specs knowledge overall. After doing a bit more research on the topic I can say that what I need is a GPU with more VRAM. However with the wide range of options, I'm at a loss as to know which solutions would be best for me.

I'll start off by mentioning my machine's specs:

Intel i7-9700K CPU @ 3.60GHz

16GB RAM DDR4 2666mhz

NVIDIA GeForce RTX 2060: 1920 CUDA Cores, 6GB GDDR6 VRAM

Kingston A400 SATA3 6Gb/s 480GB SSD

The scene images I attached to the post are an example of what I consider a simple scene that has been causing me these memory errors when trying to render an image above 720p. The model includes a simple exterior, a social area, and a simple bedroom. Total model polycount: around 14M.

This is the error I've been coming across. It's not shown on the image but render stops when reaching the Dedicated GPU usage limit. The model itself does take a huge chunk of it though.

On paper, the solution is simple: buy a new GPU with more VRAM or getting rid of heavy models in the scene. Or even using a bunch of proxies.

The thing is at first I thought that the reason of the high VRAM usage was the vegetation. Two high poly trees, a Forest for the grass, scattered leaves, high poly bushes, etc.. BUT, the same error still showed up even when rendering an interior scene with all vegetation hidden. Even when deleting all of it I still got the same out of memory error. This isn't the only file that has shown this same behaviour.

I've shared the model to another person that owns a 3000 series RTX GPU. (Not sure which one specifically) She also got an error. Not the same one, however. I do remember she mentioned her GPU had 8gb of VRAM.

Right now, I'm considering in buying an RTX 3060 with 12gb of VRAM, which is in an affordable price range. I do also need some insights in how CUDA Cores and VRAM play a part on these types of processes. I'll go out on a limb here and say that, to my knowledge, more CUDA cores would just affect render times, and more VRAM would allow me to render complex scenes. My GPU does not support NVLink so just buying another RTX 2060 is not an option. The RTX 3060 does support it. Maybe I'm wrong but I feel that that solution sounds overkill. At least for the type of projects I'm currently working on. When I built my PC 6GB of VRAM sounded like a decent machine for ArchViz renderings.

Anyways, I have a few questions:

If VRAM is the issue here, how can I know how much would I need? At least for FullHD renderings which is my current goal.

Maybe a model in the scene other than the vegetation is causing the issue? Or maybe a material? How can I tell which one? But as I mentioned earlier, I had the same issue with other scenes and, as far as I can remember, I did not recycle any models other than the fridge. Still if it were the fridge, it doesn't explain why I keep getting the same error when rendering the exterior or bedroom scenes.

Does more CUDA Cores reduce the amount of VRAM used?

I'm also aware that my machine runs a bit low on RAM. Will increasing my RAM from 16GB to 32GB help? Does RAM also affect how much VRAM is used?

PD: Upon writing this post, I noticed this:

GPU usage only reaches up to about 50% but only when moving the viewport.

Any idea of what tests I could run to find the real issue? Because there is a huge difference in the amount of VRAM used between the first and second images, and I'm not running any other GPU intensive software.

[James Vella]

Those scenes look far too heavy for your GPU. Remember also Windows 10 takes 2GB of your video card by default so you only have 4GB left.

Windows Task Manager will not show you the correct usage for GPU, you need to use HWinfo

Try running the render while watching hwinfo and report back your usage, more than likely you will need more GPU Ram.

 

[Adrian GT]

Done running the tests.

no MAX running

MAX idle

After render fail

I can clearly see now it's a VRAM problem. There is one thing that does not make sense to me. When MAX was idle right before rendering, the current GPU VRAM usage marked around 80%. After the render failed it marked around 50%. Why is that?

And thank you for the reply. I feel a bit more confident that buying a better GPU is the right track here. I still have a few questions though:

• How does RAM play a role in GPU rendering? Will increasing my RAM help my GPU using less VRAM?
• Should I save and work on my files in a HDD or SSD? Apart from launch speeds, how does that affect the render process?
• The scene's screeshots in the original post show the kind of projects I'm currently working on. Given that info, how much VRAM would you reccomend for Full HD renders?
• Should I focus on getting a GPU with more CUDA Cores or more VRAM? I'm honestly not sure on which aspect to focus on. Render times at the moment are not my priority. Correct me if I'm wrong but I think CUDA Cores only affect render times and VRAM the overall size of the model that the GPU is able to render.

[James Vella]

• Increasing your RAM will not help your VRAM. When GPU rendering if you run out of VRAM thats it, game over.
• HDD or SSD its your choice. SSD is faster obviously - loading/unloading textures/proxies and any external asset. Once the render engine has loaded the external files it does not affect the render speed.
• I couldn't recommend anything but more is always better. I use a 16GB 3080 just because I am doing more GPU renders lately. Whatever you can afford go for it its worth it in the long run. Regarding the size of those scenes many things to consider, for example if you have 3GB of textures being used in the scene you need +3GB of VRAM, add this to proxies, displacements, fur, subdivisions etc it adds up quickly. Monitor the usage as you build and render your scenes and you can start to get a better idea of when to optimize and when to upgrade the hardware.
• CUDA cores = speed. VRAM = size. You are correct with your assumption.

Edited September 8, 2021 by James Vella

[Rodolfo Tanno]

In V-ray setings >  GPU Memory Management > Resize, try set "On-demand Mipmapping".