Why does Blender composite my file twice?

When I render to a Multilayered OpenEXR, Blender renders normally once using a specified amount of tiles and apparently does all needed Compositing simultaneously as I never see Blender ‘Compositing’ afterwards.

However, when I render to a ‘Singlelayered’ OpenEXR with some File Output nodes to export each Cryptomatte pass separately, Blender suddenly starts ‘Compositing’ each (!) already rendered tile, which will take minutes. How can this happen as the Compositing data is already there, since Multilayered OpenEXR apparently uses this when saving?

Can anybody please explain this to me? Thanks in advance!

This sounds odd, can we see your compositor node setup?

Got it. This happened because of the rendered image being too large (I needed a huge resolution render) for Blender to be able to do even the tiniest compositing. When I checked ‘Crop to Render Border’, the compositing only took a few seconds. :wink:

Thanks anyway!

In other things I’ve done, I noticed that blender doesn’t completely respect the outputs set in the compositor when you are rendering from render layers. For example, if you are outputting to a file output node and don’t have a composite node, blender will save a render of your file without compositing to the output folder you have set in the property editor when you are rendering an animation.

This lead me to think that maybe you were rendering an animation, but left the file output path set to the temp folder, and you were just running into some sort of storage capacity limit set to that folder. Thinking this, like a fool, I rendered the test file you sent without closing any of the programs I have running and it locked up my system as well :sweat_smile:. After hard resetting and re-rendering the file while nothing was running in the background, I was able to get it to output a 16 megabyte jpg with the depth pass. This took all of my system’s ram to do (16 gigs). I think the issue is simply that whatever library blender is using to write images needs a lot of memory in order to write files with huge resolutions.

Ooooo I hope my file didn’t crash any important programs or tasks on your computer?!
As I mentioned earlier, checking ‘Crop to Render Border’ solved 99% of the issue. Had to do some other tricks to make it even faster, but now I’m back on track! Thanks again!

No, its fine. I was just downloading some stuff in the background. Nothing important was open. I’ll just be more careful before rendering in the future.