sRGB textures to ACEScg?

[SonyBoy]

If I have sRGB textures but want to work in ACES, what's the correct workflow.

I'm consistently blown away by how confusing and complicated color management is, and how little COMPREHENSIVE help there is for us ordinary grunts in understanding every step of the correct setup and worflow, with enough IF and THEN caveats to cover all possible scenarios.

If you're working right through an ACES pipeline from texture creation to final output it seems fairly obvious, but what if you're starting with assets that were NOT created for ACEScg rendering?

[hermit.crab]

If you're working right through an ACES pipeline from texture creation to final output it seems fairly obvious, but what if you're starting with assets that were NOT created for ACEScg rendering?

You just need to state that those textures are sRGB in the Color Space rollout. This way V-Ray knows what it's working with. This tutorial is quite detailed, check it out.

[SonyBoy]

Thanks, but I've seen that page before and it's a perfect example of the type of thing I'm talking about. It contains some good -- and some clear -- information. However, it also glosses over or omits many things, making setup sound more straightforward than it is. Here's an example:

"The V-Ray Frame Buffer provides a filmic tonemap correction in AMPAS mode that emulates the OCIO display transformation, which can be used instead of an OCIO configuration."

What on earth is that about? I assume this is just saying that you can apply a display color transformation with this tonemap layer, but I'm not sure. This is pretty typical of documentation, which seem to be consistently written by people who don't know how to write without leaving any ambiguity.

That page also doesn't explicitly explain how to interpret color maps, which is of course what my original post asked about. So, this is hardly a comprehensive page for something that is so important. The video it links to is also incredibly simplistic, and uses Maya 2018 (that's SEVEN versions ago) for its example. The color management settings shown aren't even the same any more, with the use OCIO checkbox having since been removed.

There are just a bewildering number of inputs and outputs with color management, and getting even one of these settings wrong can mean you're NOT working in the color pipeline that you think you are.

[Pixelcon]

A sample scene or vfb preset from chaos with the correct settings as a starting point would have been nice. Or perhaps a file we can check our saved-out image against to make sure we're getting a 'correct' result. I can follow as many guides as there are out there, but without some ground-truth to compare against, my confidence isn't what it needs to be to use ACES.

[SonyBoy]

Another basic piece of information that I never seem to see explained anywhere is whether pure R,G and B values are ever affected by color management. Can anyone speak to that? If I'm using RGB mattes, do I need to ensure those are interpreted with none or "preserve values", should they be transformed upon input to comp in the same way as any other RGB content, or doesn't it matter either way?

[hermit.crab]

"The V-Ray Frame Buffer provides a filmic tonemap correction in AMPAS mode that emulates the OCIO display transformation, which can be used instead of an OCIO configuration."

AMPAS stands for "Academy of Motion Picture Arts and Sciences" a.k.a the guys that made the ACES standard.

What on earth is that about? I assume this is just saying that you can apply a display color transformation with this tonemap layer, but I'm not sure.

Yes.

That page also doesn't explicitly explain how to interpret color maps, which is of course what my original post asked about.

Well, I don't think that's something you can eyeball. Whether a color is slightly brighter or darker won't let you deduce its color space. It depends on where the images came from, if they are raw, or if they have some display correction baked. This "meta" info should either be stated or you should know about it from the people who provide the images.

There are just a bewildering number of inputs and outputs with color management, and getting even one of these settings wrong can mean you're NOT working in the color pipeline that you think you are.

Stick to the tutorial and you should be fine.

Another basic piece of information that I never seem to see explained anywhere is whether pure R,G and B values are ever affected by color management.

Not sure what you mean by this, but when you click on the color palette of the i.e. diffuse color, you can see there's a Mixing Color Space, which lets you choose how to display the color: as data (pure), in the chosen rendering space, or with a view transform.

Can anyone speak to that? If I'm using RGB mattes, do I need to ensure those are interpreted with none or "preserve values", should they be transformed upon input to comp in the same way as any other RGB content, or doesn't it matter either way?

Technical passes are not affected by the display correction in the VFB, even when baking it. If you're not baking, in your comp, you shouldn't apply any corrections to them since it would destroy the data.

[Pixelcon]

Sorry to interject but it's on topic:
The Maya Tutorial says "The V-Ray Frame Buffer provides a filmic tonemap correction in AMPAS mode that emulates the OCIO display transformation, which can be used instead of an OCIO configuration."

However the same page directed at Max users says no such thing. Does this mean the Ampas filmic tonemapping mode in Max will not achieve the same results?

[piotrus3333]

Filmic tonemap AMPAS (A) is not even close to ACES 1.3 RGC (B) (both sRGB display) in VRay 7.

[Pixelcon]

Filmic tonemap AMPAS (A) is not even close to ACES 1.3 RGC (B) (both sRGB display) in VRay 7.

Right...So the Vray docs are wrong? How the hell do we know what to do when there's so much conflicting information out there...

[SonyBoy]

You can see the response I got... "you have enough information, stick to the tutorial, even though it's clear from a simple Google search that the vast majority of people are completely confused by ACES, how to properly apply it, what it can and can't do, what it's supposed to be for, when you should and shouldn't use it". I just gave up trying again after working -- and rendering -- in ACES for weeks because at the end of the output phase I could not get consistent color out of After Effects. So I'm switching back to a more predictable linear workflow. Yes, After Effects sucks we know this. But this is part of the problem. CG production ALWAYS goes through multiple applications, and I'm yet to see comprehensive documentation and workflow information from any entity that takes you through the ENTIRE process with a specific set of tools and shows how to get correct results. This is obviously beyond Chaos's purview, but on the other hand it always feels like Chaos is afraid to give any information that doesn't pertain directly to its products. This is not helpful at all to its user base.

[Pixelcon]

You can see the response I got... "you have enough information, stick to the tutorial, even though it's clear from a simple Google search that the vast majority of people are completely confused by ACES, how to properly apply it, what it can and can't do, what it's supposed to be for, when you should and shouldn't use it". I just gave up trying again after working -- and rendering -- in ACES for weeks because at the end of the output phase I could not get consistent color out of After Effects. So I'm switching back to a more predictable linear workflow. Yes, After Effects sucks we know this. But this is part of the problem. CG production ALWAYS goes through multiple applications, and I'm yet to see comprehensive documentation and workflow information from any entity that takes you through the ENTIRE process with a specific set of tools and shows how to get correct results. This is obviously beyond Chaos's purview, but on the other hand it always feels like Chaos is afraid to give any information that doesn't pertain directly to its products. This is not helpful at all to its user base.

Given how long and how confusing this topic has been for so many years, it's bizarre how difficult this has to be. One look at the OCIO stuff or anything piotrus3333 talks about and I feel like an utter moron. How can there there not be a step by step set of instructions that is correct AND simple to follow.

[SonyBoy]

Given how long and how confusing this topic has been for so many years, it's bizarre how difficult this has to be. One look at the OCIO stuff or anything piotrus3333 talks about and I feel like an utter moron. How can there there not be a step by step set of instructions that is correct AND simple to follow.

Totally. It's clear that almost nobody understands it properly, whilst there are a lot of people who claim that they do who are putting out half baked training and tutorials, so the signal to noise ratio is low. The number of tutorials I've found that claim to show you how to work in AE in ACES for example, but which totally miss important details such as how to output a movie file for this or that purpose, glossing over which color space to be comping in and/or which settings you MUST get right. It doesn't help that Adobe doesn't give a monkey's about CG or color management in general. Photoshop's is essentially non existent, the implemenation in After Effects now is just ludicrously opaque and confusing. Then even with the limited training material that there is out there, you're constantly butting up against the fact that a lot of it is geared toward a live action pipeline rather than a fully CG one (although that shouldn't matter), so they spend half the time demonstrating color management on live footage, which has nothing to do with CG and is a waste of time. A lot of the material is technical rather than practical in nature (I'm so sick of looking at color gamut illustrations and reading about the big picture of ACES), with very little in the way of full start-to-finish practical examples. I'm still not even clear what the primary purpose of ACES is -- I've seen it claimed to both be for a greater color gamut, and also to standardize color values throughout a pipeline. Which is it? I've been doing CG for 20+ years and color management in general has always been so much voodoo to me, but ACES has made it worse now because of the way it's presented as the great unifying solution. If it's that simple, why is it so difficult? All I need is a simple set of input-output instructions that are clear to follow.

[piotrus3333]

I have to admit that the marketing and myths around ACES caused a lot of harm to the cgi industry. most of us do not need it at all - true, rendering in acescg is more pbr than rendering in srgb (BT.709 or rec709) but it would be safe to assume that if you don't know what the difference is - you do not need to worry about it too much.

I guess what most cgi people like about ACES is just the "look" (so how data from the renderer is transformed to look good on a display) - and this can be pretty much boiled down to a lut you slap on srgb output from VRay.

[Pixelcon]

If it's that simple, why is it so difficult?

True that.

[piotrus3333]

another point about ACES and its marketing: some professionals were so convinced of it's magic that quite a lot of big productions have quite unsightly blue light out-of-gamut issues ("looks bad but it is aces so I guess it is good after all"). there is a collection of frames floating around somewhere that I can not find at the moment but what I remember and can quickly double check is Obi-Wan tv show, episode 3, laser sword duel around 35:17 mark.