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I would like to output both images where the color management (like filmic) is applied and save an object-ID pass. The catch is, the object-ID pass needs to contain the object as absolute white #FFFFFF. This of course doesn't work since the color management is set globally for the project and the "File Output"-node always applies the color management.

Is there any way to circumvent this? Since performance is critical I can't do a second render with switched color management.

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  • $\begingroup$ Maybe @troy_s can tell what input value is mapped to white by filmic. $\endgroup$
    – John
    Oct 22, 2017 at 14:05
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    $\begingroup$ I can. I'm curious about this odd limitation however with regards to object-ID passes? I'm completely a worthless hack on this front, so any further explanation you can offer would be appreciated. The minimum and maximum values are calculated 2^stops * middleGreyPegPoint. In Filmic's case, this would be 2^-10 * 0.18 for minimum and 2^6.5 * 0.18 for maximum. The object ID pass relying on a display referred value just seems batpoop wrong though. $\endgroup$
    – troy_s
    Oct 22, 2017 at 18:14
  • $\begingroup$ @troy_s thank you for your help. The pass itself doesn't rely on it, the output to a file however does. The way I have to use the data requires it to be saved in a format like .png (in general no format that supports the output of the raw data like .exr or .hdr). Therefore I need some hack to get the white value from the object-ID pass to be stored as actual white color. $\endgroup$
    – John
    Oct 22, 2017 at 21:37
  • $\begingroup$ @troy_s as far as I can tell, blender has no way of disabling color management (or using linear) for selected file output nodes. $\endgroup$
    – John
    Oct 22, 2017 at 21:39
  • $\begingroup$ @troy_s value works like a charm. Still a dirty hack though. $\endgroup$
    – John
    Oct 22, 2017 at 21:41

2 Answers 2

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I'm not sure about the old versions, but now blender supports overriding scene color management for the file output node.

Overriding default scene color management

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Ok I found a way to do it. Instead of doing an alpha over with the ID Mask between black and white, I use black and a value node. The value node is set to a high value, high enough for the filmic color space transformation to map it to the maximum value 255/#FFFFFF in the output.

This has two problems though, 1) it depends on the "alpha over"-node to accept higher values than usually available (this should be ok, since internal representation is floating point), 2) I just took some high value instead of basing it on what value is mapped to white.

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