Default_view_transform Houdini useage

Discussions - Using ACES VFX
1

Looking at Houdini 20.5 OCIO config and how it deals with OCIO in general i found 3 oddities (Houdini/Karma)

  1. Houdini defaults to rendering in linear/rec709, i wonder why they do this instead of acescg

  2. It defaults to using “un-tonemapped” as the default view transform, looks like they want to match “legacy” colormanagement here by default…

  3. instead if using the first defined colorspace in active_views like I would expect , Houdini uses the default_view_transform entry instead.

I find especially 3) to be confusing and I dont understand why they do this, default view transform is not ment to be actually the first / default view transform but its used as a connecting space between scene and display reffered colorspaces, right?

from the docs

The default view transform is the view transform that is used if a ColorSpaceTransform needs to convert between a scene-referred and display-referred colorspace. If this key is missing, the first view transform in the config is used.

anyone knows if this is intentional or is that a design mistake by SideFX?

2

I filed a bug in August for #2 and #3 since it’s the same problem. I never got a follow-up except to tell me that they added my name to a previous bug that was already filed. I don’t think this will be fixed before houdini-21 since it would change the look of images. I invite you to file a bug too. The more we are, the higher it gets in the priority list.

In the mean time, I changed the default_view_transform in our OCIO config to force it into ACES 1.0 - sRGB video.

As for #1, I have noticed a few weird behaviors in Houdini’s color management. Some images are loaded in ACES instead of ACEScg and such. But I never took the time to pin point the problem and report it to them.