Hi, I'm having some issues when using a background image in a USD camera. I will try to explain what I'm currently doing, and hopefully someone will have the correct answer...

I'm using an OCIO config (slightly modified Academy Color Encoding System - Studio Config with some custom rules)
the rules I'm adding are regex based and are really very basic: find patterns like srgb or exr extension, stuff like that. The rules are indeed working fine.
For all my textures everything is being handled by the File Color Space parameter in the mtlX Image nodes
I'm using the ACES 1.0 - SDR Video view transform (which as far as I know is the recommended one to avoid clamping of the highlights and to interpret the lights and shaders in a more "realistic" way)

Up to here, everything works perfectly: my renders look correct and all that jazz. But whenever I try to load a background image in the USD camera, whenever I switch to the ACES 1.0 - SDR Video view transform, the background also gets affected and becomes darker. I would like the background image to be unaffected by the view transform. I thought that setting a rule for the backplate and setting the color profile to sRGB - Display would be enough to avoid this, but unfortunately, that is not working. If I switch to un-tone-mapped, the background colors look correct, but then my highlights are not correctly compressed.

Does anyone know if there's a way to use the ACES 1.0 - SDR Video view transform without affecting the background image?

I don't want the plate to be rendered, it is just a reference for matching the lighting of the backplate, but having it darkened by the view transform is almost useless to really match the intensity and saturation of the lights.

Any help would be really appreciated.

Btw, I'm using Houdini 20.5

Hmmm, I find it really strange that no one has this same problem or a solution for it, but in the meantime, how are you guys working with background plates to match the lighting? Perhaps I'm simply not using the right tools and there's a workaround for my issue.

We are using exr files with ACEScg colorspace for everything getting imported into Houdini, so artist don't have to deal with colorspace. But yes improvements should be added, so it will be easy to just invert the Display view transform on the backplate as it is in Maya.

Heileif
We are using exr files with ACEScg colorspace for everything getting imported into Houdini, so artist don't have to deal with colorspace. But yes improvements should be added, so it will be easy to just invert the Display view transform on the backplate as it is in Maya.

For us using exr as backgrounds would be way too heavy, that's why we are using proxy png sequences. as a side note, I revisited the custom rules and now everything is working fine: an inverse view transform is applied to the background images so when I select the ACES 1.0 - SDR Video view transform, everything looks correct, so mistery solved, it was a user error, not a Houdini error.

That said, having the ability to change the color space of the background images would be nice, instead of relying on custom rules and file names.

Good to hear it'solved

Regarding the exr files being heavy. With dwaa compression, you can get the files tiny and still looking good. That's what we are doing on our background plates that is used in Maya(anim) and Houdini. The big exr files with zip compression is only used in Nuke at the end.