Multichannel EXR do not save correctly

[kosso_olli]

Hey guys,
I have a few scenes here where the finished render does not save correctly as Multichannel EXR. The resulting EXR is only about 30kb in size and saving only takes 2 seconds.
Please see attached files for settings.
Saving manually via the Save icon in the VFB does work. It takes longer of course, and the resulting EXR is a few hundred MB, which seems correct.
File is around 4000x4000px. 3dsMax 2023, V-Ray 6.00.20.

[vladimir_krastev]

Hi, thanks for posting. If you want 32bits exr you should enable the checker visible in your screen grab. Saving vrimg will always default to 32bits (docs page). But there could be something else since you are describing a huge difference in file sizes.

[kosso_olli]

The file is broken, too. There is no way to open it in all the software I tried.

[vladimir_krastev]

Is this happening in every scene even a new simple scene? Have you tried to re-install V-Ray? Have you tried saving in a different folder?

[kosso_olli]

Is this happening in every scene even a new simple scene? Have you tried to re-install V-Ray? Have you tried saving in a different folder?

It occured on a number of scenes that were created a few days ago.
I tried saving to different locations, not difference. Files are still 30kb in size.
Will keep investigating.

[kosso_olli]

Happened again today on various files from different projects.
It seems to be resolution dependent. Small res of around 2k works fine, full res saves a Multichannel EXR of a few Kilobytes which is broken.
Saving manually through the VFB does work fine, still. Why is automatic saving after render broken?

To be honest, I have not used Multichannel EXR for at least 10 years, but now I have to because of Cryptomatte. Adn I just can't get it to save a full res file.

[fixeighted]

Just a thought (as it works fine here) but do you have the most recent version of the exr plugin? Maybe something changed.
Or, if you only need the Crypto, then maybe try a simple shader on everything and only output that one element, to see if that works.

[kosso_olli]

Is there anything thats needs to be installed, apart from V-Ray?

[kosso_olli]

I think I found the issue.

The Multichannel EXR is not saved correctly when a render region is active (which is on nearly 75% of our jobs) and the V-Ray OptionRE parameter EXR data window is set to "region", which is the default. As soon as that parameter is set to "whole image", I get working Multichannel EXR.
Tested this on different scenes, setting EXR data window to whole image via OptionRE fixes the issue.
Also, I was able to reproduce this on any machine in our render network, as well as across different versions of V-Ray. Tested on Max 2023 with V-Ray 6.00.20 and on Max 2025 with V-Ray 6.20.06

Somehow, this is still tied to render resolution. At quarter resolution I get working files, even if data window is set to region. I do not know why.
It seems at full res the wrong region is saved or corrupted.
Maybe one of the devs or support people can try to reproduce this? I have scene files illustrating the problem.

[Joelaff]

Interesting. I tend to keep the Data Window set to Auto, which will make the data window based on the black alpha, which is usually faster to deal with in post (at least in Nuke and Fusion that use the data window). This seems to work correctly with or without a region (at least a Vary VFB region. I don't use Max's regions very often).

Note I have not tried renders anywhere near as big as the still you do, though.

[kosso_olli]

Same here, we would like to use data window set to region or auto because of speed. Writing and reading EXR with data window set to whole image makes things noticably slower for us.

[vladimir_krastev]

Hi kosso_olli I tested your described setup. I added all render elements and followed your steps but on my setup everything seems to work fine. The exr saves with all channels as expected.
Do you mind sending your scene for a test? You can do that here or trough the support contact form.
Here is my test:

[kosso_olli]

Hi kosso_olli I tested your described setup. I added all render elements and followed your steps but on my setup everything seems to work fine. The exr saves with all channels as expected.
Do you mind sending your scene for a test? You can do that here or trough the support contact form.
Here is my test:

I sent you a private message with one of the scene files illustrating the problem.
As soon as you delete the OptionRE element, a corrupted EXR should be written.
If you have any questions, feel free to ask.

[kosso_olli]

A freelancer we have been booking for years has excatly the same problem recently: Corrupted Multichannel EXR when saving region renders at very high res. The files are below 30kb as well.

Granted, it is the same project, but a totally different machine and network.
Something is severely broken with saving of Multichannel EXR in very high resolution.

[vladimir_krastev]

If it works in a new simple scene for example a few cosmos models and a light (this was my test setup yesterday and everything worked ok) then there is something in your specific scene that is triggering the issue or there is something else outside 3ds Max/V-Ray. I will look into the scene now and hopefully find something.
Also from your first post I noticed you are not using the latest official version of V-Ray found here. Please try to download and install it to see if this will resolve the issue.