CL_DEVICE_NOT_FOUND with Nvidia Graphic Cards

[Chatnori]

New to BlendLuxCore but encountered this issue after installation.
The render engine cannot start and report this: OpenCL driver API error (code: -1, file:D:\a\LuxCore\LuxCore\src\luxrays\devices\ocldevice.cpp, line: 89): CL_DEVICE_NOT_FOUND, which points to a path non-exist. OpenCL device can be detected by other programs.

The environment I am using is:
Blender 4.5.1 LTS (Tried 4.3, but reproduced the same issue)
LuxCoreRender 2.10.1
Windows 10 19045.6093
Nvidia 4090, NVIDIA Studio Driver 577.00

I searched this issue and found it happen to others as well (see #932), but did not find a good solution.

[CodeFHD]

Hello,

Directly (!) after installation this error is known to me. The search for OpenCL devices needs to be triggered once, but there is no "post-installation" handler to execute this.
It should work after restarting Blender.

Please let me know if this solved your problem or if the issue persists.

I don't think LuxCoreRender/BlendLuxCore#932 can be considered related due to large-scale dependency updates in the meantime.

[Chatnori]

Hello CodeFHD, thank you for your advice.

I have attempted to

1. restart Blender
2. restart Windows
3. uninstall and reinstall Blender 4.5.1
   however, none of which worked.

I even set the same environment for one of my colleagues, on his workstation with the same specs (RTX 4090, Windows 11, Blender 4.5, Luxcore 2.10).
And the same problem occured.

But I finally tried to circumvent this problem by setting the environment on another RTX 4070 desktop.
Blender 4.5.1 LTS
LuxCoreRender 2.10.1
Windows 10 19045.6093
Nvidia 4070, NVIDIA Game Ready 576.80

No solution has been found yet for 4090 devices. Is that a difference?

[CodeFHD]

Hello, sorry for the delayed response.
I can currently only think of two things to check and try to see if this is driver related:

1. The differences between you setup was Studio and Game ready driver. Maybe they were not in quite the same state. Can you try again with latest drivers on the 4090 system. (FYI, I only this week set up two PCs with Quadro cards, bit older models but no "game ready" drivers either.)
2. Can you check if it happens with both OCL and CUDA backends? You can select this in the addon preferences.
   Thanks!

[Chatnori]

Hello,

I have checked your suggestions and

1. Update my 4090 card to Game Ready 581.15 (Released on Aug 28, 2025), and unfortunately no change is observed.
2. The OpenCL and CUDA switch in add-on preferences is something I tried at first and it troubled me with no difference at all. I assume when switched to CUDA we should not use openCL any more? Seemingly not the case.

By far that is everything I could provide.

Thank you !

[CodeFHD]

Hi,

about point 2: With an nvidia GPU, the CUDA/OptiX backend is preferred because it will generally lead to higher performance, so there is no reason to stick to OpenCL.

Im am not sure I understood the second part of it though, "it troubled me with no difference at all".

So is there some error as well when CUDA is selected?

I looked briefly at the line that throws the error, but it is not an obvious one to me. The line in question tries to get the number of OCL devices of all types, so this indicates nothing is detected. Seems strange, and that there is something else wrong fundamentally...

[Chatnori]

Hello,

I expect that when switched to CUDA API, we do not need OpenCL and CL device detect any more, which I am not very sure. But it keeps that no device available and CL_DEVICE_NOT_FOUND error. I hope these attachments explain it well.