Failed to Invoke Render

[armadillu]

Describe the bug
When I try to start a render, I get a warning message "Failed to Invoke Render". This is on widows 10 (latest update) Blender 4.2. The same file renders fine (through the plugin) on macos and Blender 4.2.

Session Log File

log 15-08-2025 08-43-17.621735.txt
log 15-08-2025 09-02-10.348173.txt

To Reproduce
Steps to reproduce the behavior:
1-Open blender file.
2-Select a few cameras to render from.
3-Go to render menu, choose "render multiple cameras"
4-warning message shows up, no render is started

Expected behavior
start the renders for the selected cams

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: windows 10
• blender 4.2LTS

Additional context

[ivan-perevala]

Hi, @armadillu

What I see is that for whatever reason eval_cameras is unable to properly evaluate camera queue. According to log files this may happen for 2 reasons:

• No cameras selected (which is not true)
• Camera angles mask cuts off all cameras, so it can't continue execution (which I would like to know how can possibly happen)

I tried the exact steps but unfortunatelly, was unable to reproduce it.

Also, from #3 experience, I would like to ask you to turn off all the other extensions and try again. Some incompatible extensions may interrupt Multiple Camera Render execution process.

I sending you my test file for this case:

TestFile_4.zip

Would be nice if you can modify it to the state where the addon works as in OP.

Thank you,
Ivan

[armadillu]

I have some more feedback; I tried multiple times to make it work by closing blender, starting again, loading the file and rendering... but the same error came up.

But then I tried loading another blender file and rendering with the plugin, and it worked on that file. Then, without closing blender, I opened up again the original file (that didn't render to begin with) and then the multiple camera rendering worked! It's rendering right now. Keep in mind the file was not modified (ie saved); with the very same file it failed and it worked without other changes... So it seems to be some internal state of blender that triggers this bug. I have to say it also happened on macos a couple of times, but usually quitting blender and relaunching it fixed the issue.

This is the first time (on windows) where I could not make it render from a fresh start.

[ivan-perevala]

@armadillu ,I still can't reproduce a situation of render failure. I tried many possible scenarios of scene configuration, camera options, etc.

By the way, I found another issue which might be related: the latest version would fail even on a correct scene configuration after one failed invocation. This would be fixed in the next patch release.

Anyway, as far as the issue is still not reproduced, I can't figure out a cause. If you can share a specific file which causes the failure, this would help a lot. If not, please check the settings and start scene conditions of this specific file and create a minimal reproducible file for this use case.

Thank you,
Ivan

[armadillu]

Hey thanks for looking into it!
I haven't been able to make it happen again, it's been working great these last days.
If I get it to happen again, I will try keep a copy of the file untouched (although as I told you, the same exact file behaved differently on two different computers) to see if you can find the trigger.
thanks again!