Rendering in 3ds Max VRay GPU GUI at least two times faster vs VRay GPU Standalone?

[petr_leontev]

We want to start using .vrscene at scale but we see a big discrepancy in terms of total rendering time. VRay Standalone seems much slower when rendering the same camera view we are using in GUI mode.

1. We are using V-Ray GPU
2. We've noticed that light cache is being built MUCH slower (like 2x slower)
3. Result image is also DARKER when using Standalone version than what we are getting in GUI mode...

How can we understand what is going on? I can share the scene.

[petr_leontev]

In particular, VRay Standalone RTX engine is slower, CUDA is a bit better...

[hermit.crab]

Best you send the scene in question so we can do some testing.

[petr_leontev]

I've sent DM with the link to the scene.

[hermit.crab]

Thanks. After a bit of testing, I can confirm there's a slowdown when using GPU with STD (indeed, the Light Cache calculation). I need to do some further testing to determine what's causing it and if it can be bypassed. I will write again whenever I have more info.

Regarding the darkening - when exporting a fresh .vrscene from the AI47_010.max file (I switch to V-Ray GPU, enable RTX, and export), I get identical results.
I looked at the provided .vrscene (AI47_010.vrscene), and it seems to have very different settings, particularly for the Color Mapping (for example, Gamma is set to 1, and the Mode is set to Exponential, etc; Sub-pixel mapping is off, etc.). Those settings are not the same as the ones saved in the .max file and surely cause the difference.

[petr_leontev]

Thank you, I will take a look at the export procedure.

[hermit.crab]

Just letting you know that we'll log the slowdown issue so that the devs can troubleshoot further. I don't think there's a workaround in your case, except using CUDA instead.

[petr_leontev]

Oh, I see. CUDA then. Any ETA on when the patch is going to be released?

[petr_leontev]

Hey hermit.crab Thank you for support!

I've just sent you the same scene. I've just reexported it to .vrscene with all settings using VRay exporter tool in 3ds max 2025 (default settings).

When using VRay Standalone I still can't match GUI render output (via Render Setup -> Render). I've also attached the example renders (you can find them in standalone_renders and gui_renders) so you can take a look at them.

I used this command to produce renders. I didn't edit .vrscene after export.

vray.exe -sceneFile="#3873660 office interiors 10\\AI47_010.vrscene" -imgFile="eval_renders\\render.png" -camera="AI47_010_VRayCam001" -rtEngine=5

Please let me know how can we match GUI renders?

[hermit.crab]

Hey hermit.crab Thank you for support!

I've just sent you the same scene. I've just reexported it to .vrscene with all settings using VRay exporter tool in 3ds max 2025 (default settings).

When using VRay Standalone I still can't match GUI render output (via Render Setup -> Render). I've also attached the example renders (you can find them in standalone_renders and gui_renders) so you can take a look at them.

Please let me know how can we match GUI renders?

Could you send it again? The message is empty.

[petr_leontev]

hermit.crab

As per your recommendation adding -displaySRGB=1 when using V-Ray Standalone definitely helps a lot but I can't still match GUI render precisely I'm surprised this flag affects output. It should only affect what is being Displayed, right?

Seems like some other flags are also missing? Please have a look at the attached files.

[petr_leontev]

hermit.crab Nvm, I've redone the experiment and now Standalone render almost matches GUI one.

My worry is should we provide some other flags to Standalone render in general to match GUI output i.e. displayLUT or displayOCIO?

Would it be possible to double check with engineers on what Flags are passed to V-Ray when rendering from GUI?

[hermit.crab]

hermit.crab Nvm, I've redone the experiment and now Standalone render almost matches GUI one.

My worry is should we provide some other flags to Standalone render in general to match GUI output i.e. displayLUT or displayOCIO?

-displayOCIO will change the VFB's display correction in STD to OCIO.
-displyLUT is depricated (leftover from VFB1).

hermit.crab
As per your recommendation adding -displaySRGB=1 when using V-Ray Standalone definitely helps a lot but I can't still match GUI render precisely I'm surprised this flag affects output. It should only affect what is being Displayed, right?

Seems like some other flags are also missing? Please have a look at the attached files.

You are saving 8-bit images, meaning that in STD, you need that flag to add the necessary gamma correction. In 3ds Max GUI, this is automatically done through 3ds Max.

I'm getting identical images like that. Please compare the images via ChaosPlayer or Nuke, rather than Windows Photo Viewer (it has its own display options, and sometimes it confuses comparisons).

[petr_leontev]

Amazing hermit.crab. I believe now I can move to testing VRay Standalone on Linux!
thank you for help!