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Chats
Hey there,

Mplay and Renderview in Houdini are displaying linear .exr files with the OCIO ACES Rec 709 view transform differently than Nuke and the Redshift Renderview display them.

For example I am rendering a frame in Redshift and viewing it with the Rec 709 ACES display transform and in Nuke and Redshift Renderview the images look identical, and there is lots of detail especially in the shadowed areas, however when I display the exact same .exr file (rendered by Redshift) in Mplay with the ACES Rec 709 view transform it looks different, especially in the darks; a lot of the detail is being lost in the blacks and shadow areas to the point where I can't use it for colour critical work.

I am using Arch Linux with the OCIO and OCIO_ACTIVE_VIEWS env variables set. I'm using ACES v1.1 config.

Is there any obvious reason why Mplay would display the linear .exr differently with the same view transform applied?
I really love using Mplay to preview renders but I have to be able to trust that what I'm looking at exactly matches what I will see in Nuke and other software using OCIO and ACES.

Cheers!
Chats
Just bumping this thread.

It's super important to my colour critical work to get parity between the Houdini Render View/Mplay, and Nuke and Redshift Renderview.
As stated above, Redshift Renderview and Nuke display linear .exr files identically with the ACES Rec 709 Display Transform, but Houdini Render View and Mplay looks different displaying the same linear exr with the ACES Rec 709 Display Transform, especially in dark shadow areas where so much detail get's crushed and is lost.

It's possible I'm doing something wrong my end but I can't think of what it could be.

Cheers!
travisrogers
I'm also curious about this though I'm using Octane. Unfortunately there is no view transform in the Octane IPR at the moment so I can not truly determine the accuracy of MPlay, fortunately I am able to get some sense of how the final render will look in ACES with MPlay, however when I open the ACES renders into Affinity Photo (and or Photoshop) and apply an OCIO transform the images show a significant red cast and the blacks are less crushed than are displayed in MPlay. I realize that all the DCC and rendering apps are still working on proper ACES implementation, however given that everything is partially implemented at the moment it's difficult to tell which one is right when they all differ!

Attached are two images, the blueish one is a screen shot from MPlay displaying the render through ACES 1.2 OCIO, the reddish version is the same image rendered out from Houdini with Octane as Multilayer EXR ACES and transformed in Affinity Photo. MC, I'm feeling your pain!


Best / Travis
jedfrechette
Are you sure those renders are actually ACES and not ACEScg? That kind of reddish tint is the kind of thing that happens when your primaries are mixed up.
travisrogers
Hi jedfrechette,

Thanks for the reply. The current implementation of ACES in Octane saves renders as ACES2065 on export only, no view transform (why I was employing MPlay). There is no option unfortunately yet to save as ACEScg. It’s possible that the implementation is somehow off on Octane’s end, but who’s to say. Interesting to hear though that this is a recognizable problem. I’m going to post this on the Octane forum to see I I can’t get some more insight from the dev team.

Best / Travis
Chats
Bumping this thread again..

Here's a screenshot of a cropped render linear .exr being displayed in Nuke with the (Aces 1.1) Rec 709 display transform, right next to the same .exr being displayed in Mplay with the Rec 709 display transform:


See how all the detail in the shadow area beneath the car and also along the wall of the tyre are being almost completely crushed to black in the Mplay viewer, which displays the same in the Renderview inside Houdini.

I'm using the Aces 1.1 default OCIO config file.
In that config file, the scene_linear role is set to: ACES - ACEScg
My system $OCIO environment variable is set correctly to point to the config file, and Houdini and Nuke are picking that config file up and are configured correctly as far as I can tell.

I've attached the .exr file in case anyone can take a look at it and please tell me if there's something I'm doing obviously wrong on my end.
Apologies to harp on about this but it's becoming more and more critical to my work to get this right..
jsmack
Sampling in the toe of the curve is definitely subpar when viewing through OCIO display. What surprised me, is that even applying the OCIO transform in VEX with 32 bit color using a VOP COP has clipped shadows as compared to other software. I have compared to Affinity photo as it is the only other OCIO aware software I have at the moment.

As viewed in Affinity ACES 1.2 Rec709 ODT


Brightened screenshot


As viewed in Houdini ACES 1.2 Rec709 ODT


Brightened screenshot


OCIO Transform in VOP COP


Brightened screenshot
martinkindl83
so where does this brings us?
Do we have a problem or its all good?
Chats
I'm not sure technically what the issue is but from a practical standpoint it's definitely problematic for me because it means I can't trust what I see in the Renderview through the OCIO display transform.. since it looks different than when viewed in other software such as Nuke with the same OCIO display.
As mentioned the dark areas lose a lot of detail in the Mplay and Houdini Renderview
twod
Chats
I'm not sure technically what the issue is but from a practical standpoint it's definitely problematic for me because it means I can't trust what I see in the Renderview through the OCIO display transform.. since it looks different than when viewed in other software such as Nuke with the same OCIO display.
As mentioned the dark areas lose a lot of detail in the Mplay and Houdini Renderview

This was fixed in 18.5.379. Edit: and 18.0.624.
Chats
Oh awesome, thanks twod I'm looking forward to checking it out!
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