OCIOIPNode mode that functions like an OCIOFileTransform node from Nuke

[KevinJW]

Currently it looks like there is no simple way to use an OCIO node to apply a file based colour transform in RV.

The OCIOIPNode node doesn't do this as there is no mechanism for passing in the file name and thus the C++ code can not setup an appropriate OCIO File Transform.

Having such a node would be helpful for support of LUT formats that OCIO supports that RV does not.

It looks like it should be possible to support it as an extension to RV's current OCIOFile mode to the OCIOIPNode node as currently there is no property for the file name, adding such an attribute would allow distinguishing from the current behaviour based on an empty string as an assumed default, would give the current behaviour and when set, the code would add the appropriately setup OCIO File Transform to the Processor.

I would think that having an additional parameter that sets the working space for the File Transform would be required so it would setup an OCIO group transform similar to how Nuke functions:

OCIOColorspaceTransform input colour space -> Working space
OCIOFileTransform apply given filename
OCIOColorspaceTransform Working space -> Output colour space

I would expect an inverse mode would inverse the whole of this transform stack.

I'm not clear if the current lack of explicit setup for the file mode is a feature, or a bug.

I am aware of a workaround involving using Looks, and context/environment variables to pass in file names, but this also requires the user have and OCIO config file with that setup

[kenmcgaugh]

Hey Kevin, that would be very useful. I also have been thinking it would be good to be able to apply view_transforms explicitly.

In the mean-time however, within python you can dynamically create an empty config in memory, add a colorspace that applies the FileTransform, and configure an OCIO node accordingly.