[Bf-committers] Updating OCIO luts in runtime

tamerlan311 tamerlan311 at gmail.com
Sun Jan 26 11:10:22 CET 2014

This feature (use LUT file without change OCIO config) available via
OCIO::FileTransform, but is not yet available in blender CAPI interface.

Please, see this thread in bf-compositor list:

And tail of this

Apply LUT node currently has the following problems:
1) Using OCIO directly, without blender CAPI.
2) Ignores that blender internally use linear color space, but LUT profiles
mainly required srgb.

2014/1/25 Björn Sonnenschein <green at unitybox.de>

> Hello,
> Is there a way to check the luts folder/the ocio config file for changes
> while runtime?
> The background is that I would like to write an lut node for the
> compositor that allows to apply lookup tables via ocio conversion like
> color grading applications like Davinci Resolve do. The purpose is to be
> able to bake color grading setups into a simple 3d lut that may be
> applied in other projects and shared with other users easily. In
> contrast to the film response curves blender provides for the final
> color space transformation, an lut node makes it possible to use luts in
> every position of the grading workflow. For Example I may use premade
> luts for my Blackmagic camera to get a good starting point for further
> grading work.
> I have already written a proof-of-concept 3D lut editor addon for
> blender.
> http://blenderartists.org/forum/showthread.php?322805-Compositor-Addon-3D-LUT-Editor
> It sets up a 3d scene with a 3d lut cube whick can be manipulated and
> then creates a rudimentary node tree that uses the position values of
> the spheres in the lut for calculating the new picture.
> Now, the real purpose of the script would be to parse a new lut file
> into the ocio folder with the corresponding values of the created 3d lut
> and also make the entry into the ocio config file and then, if you
> manipulate the the 3d lut in blender, update the lut file and then make
> ocio update the luts it has loaded so that you can get a realtime
> preview of what you do using the compositor with the lut node.
> My plan to realize the update of the lut cache would be to implement a
> function to do this into the lut node which may be accessed by the user
> to update the lut list if he has added a downloaded lut to the folder
> and also by the python api so that the script may call it.
> By the way, does anyone know how to work with .cube luts coming from
> davinci resolve in ocio properly and in which color space they have to
> be applied? I have tried this one
> http://www.captainhook.co.nz/blackmagic-cinema-camera-lut/
> by creating a new pseudo color space which interprets the input image as
> sRGB, converts it into Blender´s Linear space and then applies the lut,
> but this does not create the right results (You may simply try it out
> with the image pairs on the website if you like).
> Kind regards,
> Björn Sonnenschein
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