When I set up a scene with V-Ray GPU and set it to CUDA or CUDA+CPU, then I have to wait for Compiling Kernels - not just the first time I render, but every time I render. I haven’t installed a new driver, or V-Ray/max version between these sessions.
It’s approx 6 seconds - every time - for CUDA. And exactly the same if I restart max and render the same scene.
RTX seems to skip through it on the second render - and looks like it remembers when restarting max.
I found some older threads with seemingly the same issue, but from years back. Is this still an issue, or am I just lucky?
Windows 10 Pro. Max 2026. V-Ray GPU 7.1. NVidia Studio driver 572.16. RTX 5080.
Hi @HenrikBC
We have this issue with the new Blackwell GPUs only, we have reached out to Nvidia for assistance.
What GPUs do you use? Did you change the cache size with environment variable?
Best,
Muhammed
I have a RTX 5080 with standard 16gb mem.
I have not changed/added anything for VRay GPU in the environment variable. Are there settings you recommend trying/adding?
Sidenote: I have also noticed than my renders will go from pass 0 to pass 16 - and then start over at 0 again, then 16 (again), but then continue through the remaining passes until the render is complete - for every single frame. Checking task manager while rendering hints that I still have gigs of free mem om the GPU. Is this related to above topic - or a completely separate issue warranting its own post?
Thanks for the information. So yes, it is the issue I mentioned above. We are trying to find a solution with the help of Nvidia at the moment, I will update you if there are news on this topic.
No need, defaults work very well
Normal behavior. Adaptive lights kicks in to make rendering multiple lights faster, a lot faster overall. If you take a look at the log when it starts at pass 0 again, you will see Adaptive Lights v3 built successfully or something similar.
Best,
Muhammed
Thanks - Hope a solution is found between you + Nvidia!
And good to know about the adaptive lights - but I would humbly suggest that the info text is updated in the render window to state that that is what’s happening, instead of simply displaying pass 0-16. I won’t change the render time, but it would make me (and others, I’d reckon) feel better assured that progress is happening, just like we do when light cache is rendering and then “starting over” for the final render. Right now it just looks like it’s doing a do-over - as per my inquiry. Adding the description text during the process would be a cost-free “psychological render boost”. 
Thanks for the recommendation, I made a note about that. It shouldn’t be too hard to implement I think
I will update the thread once this is ready
Best,
Muhammed
This is now fixed with the latest studio driver. We will update it to be the new recommended driver
Best,
Muhammed
Nice - looking forward to seeing if it makes a difference!