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Error when using CUDA for a very small scene: [GPU light cache] Could not allocate buffer of size 1865MB!

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  • Error when using CUDA for a very small scene: [GPU light cache] Could not allocate buffer of size 1865MB!

    Hi!

    I am using VRay from Grasshopper to create animations. The CPU engine has been working fine for me, but it was a bit slow, and I have a GPU card idling out there. But when I switched to the CUDA backend, the rendering was always interrupted by the following error:

    Error : [GPU light cache] Could not allocate buffer of size 1865MB!
    Click image for larger version  Name:	Screenshot 2023-01-19 100428.png Views:	0 Size:	696.3 KB ID:	1170494

    Based on the suggestion in this post on the same issue, I thought it was my VRAM is not large enough. I created a minimal working example (Grasshopper script attached below) on a scene with just a simple box and a plane, but the error kept showing up when rendering in animation + CUDA mode.

    I switched back to single-frame rendering mode with the CUDA engine. I clicked `render`, and it was interrupted again by the error message above. Following the "try-it-again" suggestion in this post, I made no change and pressed `render` again in the CUDA engine, and suddenly it can render (and much faster than CPU as expected)!

    In summary, the CUDA engine must be tried twice (once failed with the GPU light cache error above and once succeeded) to work on a small example. If this is always the case, from a user's perspective, can we simply have the VRay engine automatically try it 1-5 times until it works when using the CUDA engine?

    The grasshopper file to reproduce the issue is here (why aren't we allowed to upload file with an extension of `.gh` in this forum???).

    My system info:
    HTML Code:
    VRay for Rhino 7 - 6.00.01 - Nov 3 2022  V-Ray COre - 6.00.21  V-Ray NeUI - 5.0.1
    V-Ray AppSDK - 4.00.00
    
    Windows 10, 64bit
    CPU Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz 2.70 GHz
    Quadrop M1000M, Driver 527.27​
    This is my GPU system info from the Nvidia control panel:
    HTML Code:
    [Display]
    Operating System: Windows 10 Pro, 64-bit
    DirectX version: 12.0
    GPU processor: Quadro K620
    Driver version: 496.13
    Driver Type: DCH
    Direct3D feature level: 11_0
    CUDA Cores: 384
    Core clock: 1058 MHz
    Memory data rate: 1.80 Gbps
    Memory interface: 128-bit
    Memory bandwidth: 28.80 GB/s
    Total available graphics memory: 18377 MB
    Dedicated video memory: 2048 MB DDR3
    System video memory: 0 MB
    Shared system memory: 16329 MB
    Video BIOS version: 82.07.B3.00.01
    IRQ: Not used
    Bus: PCI Express x16 Gen2
    Full Vray log can be found here. vray_log.txt

    Thank you very much for your help in advance!
    Attached Files

  • #2
    Hi, Yijiang,

    Thank you for the very clear explanation of the issue and the provided information.
    You should be able to upload .gh or other file types as .zip archives files here or send them to our Support teams by opening a new ticket.

    As you have correctly suggested, this is a memory-related error and indicates that there is not enough VRAM, for the rendering. The Nvidia Quadro M1000M and Quadro K620 both have a total of 2GB VRAM. From what I can see the animation requires 3.84GB and therefore V-Ray displays the “Could not allocate buffer of size” error message.

    Interestingly the still image on our side requires 2.4GB VRAM to be rendered. It is possible that some additional background process was running that also required VRAM and therefore the error occurred the first time you attempted to start the render.

    In cases where the available VRAM is little the projects need to be very well optimized or the CPU rendering engine can be used instead. You can find more information on project optimization in the articles below:
    Memory Usage Optimizations for GPU rendering
    Memory Usage Optimizations for CPU rendering
    V-Ray Displacement Optimizations
    CUDA out-of-mem error


    Please also kindly note that the current recommended NVIDIA driver for V-Ray GPU rendering is 526.98. This information can be found at the top of the V-Ray GPU page.

    The VRAM can be monitored from the Asset Editor > right window extension > Stats, or it can also be monitored via external tools such as GPU-Z. Note that we do not advise monitoring the memory from the task manager as the information there will not be very accurate.

    If you would prefer I would be more than happy to arrange an online meeting in order to monitor and discuss the behavior on your side. In order to arrange a TeamViewer please make sure to open a ticket from here.
    Diana Milenova | chaos.com
    Chaos Support Representative | contact us

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