I've been struggling a little with Cycles and my GeForce GTX 750 graphic card. Most of the time it works well, but when I try to work with scenes that have custom shaders (like a skin shader with multiple textures, including for displacement), I get an error, both on the viewport and at rendering:

Cancel | CUDA error: Out of memory in cuLaunchKernel(cuPathTrace, xblocks, yblocks, 1, xthreads, ythreads, 1, 0, 0, args, 0)

Or something like that. Here's a screenshot so you can check it out:

enter image description here

I'm using a PC and Windows 7, with 8Gb of RAM. I can't render this scene with GPU, but using CPU, it renders ok.

My question is: What is causing this issue? I have the latest drivers installed for my graphic card, so I have no idea what this is.

  • Have you got the experimental feature set turned on, just above where you choose whether to render with cpu or gpu? I got those sort of visual errors when I switched it on, switching back to 'supported' fixed it. – Ray Mairlot Oct 31 '14 at 18:57
  • Hey, @RayMairlot, thanks for the reply! I did render when I switch from experimental to supported, but I'm using the SSS shader in one of my shaders, which just works with the experimental feature. Maybe when SSS works with supported it will work ok, but for this particular scene, it isn't optional for me! :( – Diego de Oliveira Oct 31 '14 at 19:04
  • Not sure what version it was introduced, but certainly with 2.72b you can CPU render SSS shaders. – Ray Mairlot Oct 31 '14 at 19:09
  • @RayMairlot you are right, it works ok with CPU, which is what I did to render this scene at the end. But CPU takes more time than GPU, an this is the whole point of my question: to make this scene work with GPU and SSS shader. – Diego de Oliveira Oct 31 '14 at 19:13
up vote 5 down vote accepted

The short answer is that SSS on the GPU eats up a lot of memory, so much so that it is recommended to have more than 1 GB of memory on for your GPU. This was mentioned in one of the videos from the Blender Conference (unfortunately I can't remember which one). Updating your drivers won't really help as that can't add more memory, so for now you are stuck with having to render on the CPU. If you have multiple objects that have SSS shaders on them then you could try just rendering one at a time and then compositing them back together.

  • 1
    Thanks for the answer, @BlendingJake! For what I'm seeing, my GTX 750 has only 1Gb of memory, so the only way to solve this without touching the scene is to get a better graphic card, right? – Diego de Oliveira Oct 31 '14 at 20:09
  • Correct @DiegodeOliveira! I don't know your budget, but you could check out something like the GTX 750 ti or GTX 760 if you aren't looking to spend a crazy amount. This link has CPU/GPU SSS tests: blenderartists.org/forum/… – BlendingJake Oct 31 '14 at 20:34
  • Thanks for the link, @BlendingJake! I think that I'll try to upgrade to a GTX 760 whenever it'll be possible. – Diego de Oliveira Oct 31 '14 at 20:44
  • glad to help @DiegodeOliveira – BlendingJake Oct 31 '14 at 20:57

I assume you are using the same graphics card for both display and compute/rendering. If so you could use hundreds of megabytes to windows and applications for display purposes.

If you then attempt to render with cycles it needs to allocate another chunk of memory in order to support running a program ( cycles ) on your GPU and on top of that all the scene data and textures.

This first bit of memory we cannot accurately measure currently. But it is the case that running an experimental kernel uses significantly more memory then the normal one ( again can be multi hundreds of megabytes).

So if you are unlucky and have a 2GB graphics cards you might only be able to use 700 mb of ram for textures + the scene data ( this is what blender measures and reports ). If you go over this you might place the card into a mode where it can no longer allocate enough for displaying and this might result in artefacts like the ones you show in the screen-shot.

  • 1
    Hey, Martjin, thanks for your detailed answer! Very instructive. I didn't know about this limitation for textures plus scene data! – Diego de Oliveira Nov 3 '14 at 19:30

I have a NVidia GTX 980 ti and I have been getting the same "CUDA out of memory error" that everyone else is getting.

I have no idea what's causing it but I noticed it only occurs if the viewport is set to "rendered" when I try to render F12 a scene or animation.

Sounds like the same Issue as I have with cuCtxCreate, I found out that it hs something to do with the Memory transfer rate of the graphics card, the workaround that I did is to lower the Memory Transfer Rate offset. though I am using Linux Fedora 25 and tweak some files in order for me to lower it in nvidia X server.

  • my current transfer rate is 810Mhz both min and max

My proof of this is that I can now run GPU rendering without error, though what I'm rendering right now might not even come close to what you're rendering, Graphics card wise.

[my temp reached up to 61 in this render, with a electric fan to cool down my laptop

I have dedicated nvidia Gt640m 2Gb. by the way have you tried to check the blenders console? you might find something useful in that console that can help you.

The idea wasn't mine I'm only sharing what I experienced and hope that I could share it and help someone, Lowering your GPU's Memory Transfer Rate offset is up to you, cause to me it's like I'm playing 2 AAA games in a frying pan disguised laptop, my GPU temp reached up to 81 degree Celsius at first try no electric fan to cool off my laptop.

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