I was trying to set up an ACEScg workflow in Houdini but got confused quickly. According to this [www.toadstorm.com]:

If you have nice linear EXR textures or renders, your IDT would instead be Utility – Linear – sRGB.

Ok, so EXRs are in linear sRGB, not ACEScg, and therefore I need to convert them.

But according to Houdini doc [www.sidefx.com]:

It assumes that EXR, RAT, and HDR formats are linear (these use the ACES-Cg colorspace because that is the space assigned to the scene-linear role in the ACES-1.0.3 profile).

So EXRs are in ACES-Cg and I don't need to convert them...? So convert or not?

raincole
It assumes that EXR, RAT, and HDR formats are linear (these use the ACES-Cg colorspace because that is the space assigned to the scene-linear role in the ACES-1.0.3 profile).


So EXRs are in ACES-Cg and I don't need to convert them...? So convert or not?

It assumes they are in acescg and doesn't convert them.

If they are in sRGB/rec709 linear, then they do need to be converted. Using the proper colorspace tag in the file name will cause mantra to automatically convert them from that named space to scene_linear.

Mantra shaders can also use an ocio transform node to manually convert from an input space to the working space manually.

Converting offline may be desirable, but there is only limited support shipped with Houdini such as with imaketx or icp. Oiiotool gives more control over source and destination space.

Converting offline may be desirable, but there is only limited support shipped with Houdini such as with imaketx or icp. Oiiotool gives more control over source and destination space.

Thank you. I checked OCIO [opencolorio.readthedocs.io] and ocioconvert seems to do the work.

But I'm kinda worried that I might "double convert" a file. Is there a way to check if an exr is already in ACEScg before I convert it?

raincole
But I'm kinda worried that I might "double convert" a file. Is there a way to check if an exr is already in ACEScg before I convert it?

not that I know of.