How to deal with background layer in ACES workflow?

[gagui]

Hi

I'm working in a new ACES project and I've faced a problem when using the background layer in the VBF of Vray 5.
My rendered elements looks ok but the image loaded by background layer looks bad.

Is there any way to fix this and convert the background layer image to ACES color space?

[yavor.rubenov]

Hello,

What issues are you having - can you share some examples ?

Currently when loading background images we try to deduce their color space (we assume sRGB for 8 bit images like jpeg,png..) and then inverse it so that the background correction applies a linear image. Then the display correction layer in the VFB should bring it to the required color space.

Best regards,
Yavor

[gagui]

Well, I think with this screen cap should be pretty clear what I'm talking about.
The Background layer image in this case is displayed correctly only if I set the display correction to Gamma 2.2 but I want to look ok in OCIO for a proper ACES workflow

[Muhammed_Hamed]

but the image loaded by background layer looks bad

It looks bad because the Frame Buffer's Display correction applies the ACES ODT on it .. the image has more contrast because of tonemapping that ACES ODT uses
Your goal is to load a background image, and not have the display correction apply anything on it. So how can we do that ?
You use your ODT as IDT, this way you avoid the Tone mapping that the Display correction uses ..



Background elements need to have IDT of "Output sRGB" or "Output P3" if your monitor uses that..
This is similar to using a backplate in Nuke..

I opened your PNG in Nuke, Read/write Node has to be Scene Linear
Used an OCIO conversion node like this ,



Then saved an EXR (important) and loaded it in the Frame Buffer

[Muhammed_Hamed]

Currently when loading background images we try to deduce their color space (we assume sRGB for 8 bit images like jpeg,png..) and then inverse it so that the background correction applies a linear image. Then the display correction layer in the VFB should bring it to the required color space.

This is not gonna work, the RRT part of the ACES sRGB view transform will cause the image to have more contrast..
Best is to load the image without linearizing it, and have a drop down menu for some IDTs that people would want to use.. Output sRGB is the correct one in this case like what I explain in my post above

Same workflow if I want to load that JPEG for a backplate in Vray, I will load the image with a linear transfer function.. then use an OCIO transform node .. In = Output sRGB and Out = ACEScg
This way the backplate in the Frame Buffer will look identical to the Windows photo viewer.

[yavor.rubenov]

We already have a feature request to add custom color space options to the background layer (internal ID VMAX-11019) so this is coming sooner or later.

[Muhammed_Hamed]

Awesome!

Thank you

[gagui]

That's great! thanks

[Richard7666]

We already have a feature request to add custom color space options to the background layer (internal ID VMAX-11019) so this is coming sooner or later.

This is great. I was clumsily trying to explain this in a post I made recently; basically a way for the Background layer to be "independent" of the rest of the VFB

[Richard7666]

Is there any news on this? I see something about corrections to Background layer added in 5.2, but doesn't seem to be this colorspace feature?

[yavor.rubenov]

Unfortunately colorspace conversions didn't make it in time for the update.

[Dave_Wortley]

Any ETA on that Yavor?

[yavor.rubenov]

Sorry no ETA currently, but I can ping you when we have something in the builds.

[seandunderdale]

How do you solve this if you dont have access to Nuke?

[Muhammed_Hamed]

How do you solve this if you dont have access to Nuke?

You can use the OpenColorIOR plugin in PS or Ae to apply the transforms I mentioned in my post. You will need to save an EXR for this to work
This is the current workaround until the background layer is updated

Best,
Muhammed