Correct usage of C4D Color management?

[seth_richardson]

So there something going on with how you pick color that doesn't make much sense to me.

If I want to work in a Linear workflow with good old filmic or even say AGX. You wouldn't really need to change any settings for C4D color management nor Vray. The problem is the colors you are picking are in the wrong space.

Say I want a 40 RGB Black, well with the default thats more like 110 RGB. in order to get a 40 RGB Black in render I have to go all the way down to 5, 5, 5 RGB.

Now if I activate C4D Color Management setup for ACES I then get the correct color values for vray 40 RGB is now actually a Black not a Grey.

I am not really understanding what vray is doing. I have mainly used Octane the past few years and it doesn't really have this issue at all regardless of color management use. I am finding this setup in the current vray to be very unpredictable in that sense some insight would be great in the following areas:

1: When working in a ACES workflow what is the correct setup for Vray 6.1? I am assuming it is setting C4D Project settings to OCIO ACES.
2: When working in a AGX workflow what is the correct setup for Vray 6.1, mainly around color swatch issues?
3: When working in a sRGB/Linear Workflow what is the correct setup for Vray 6.1?

[deyan.hadzhiev]

Hi seth_richardson I'll try to answer as extensively as I can.

3: When working in a sRGB/Linear Workflow what is the correct setup for Vray 6.1?

I'll start with a brief explanation of the state of working in sRGB/Linear Workflow as this is mostly applicable for older versions of Cinema 4D (R26 and older).

Disabling the "Linear Workflow" is not really supported, as V-Ray always uses Linear sRGB or ACEScg as a render color space internally.
The "Input Color Profile" option basically determines the color transformation that will be performed on classic materials and shader color inputs. When this option is "sRGB", an sRGB -> Linear transformation is performed, when it is "Linear" no transformation is performed on the colors. Note that this does not affect the node materials which are always storing and using linear values, but the color inputs there allow the values to be previewed either as linear or as sRGB, by this button in the expanded control:

So having covered the inputs, the color management in the V-Ray render settings only determines the render color space that is going to be used, but it is important to note that even if ACEScg is selected, the color inputs in the classic materials and shaders are considered in the color space determined by the "Input Color Profile".

1: When working in a ACES workflow what is the correct setup for Vray 6.1? I am assuming it is setting C4D Project settings to OCIO ACES.

It depends on your version of Cinema 4D. If you are using older Cinema 4D version (R26 and older) there is no much choice - there is only the "Basic" color management.
For 2023 it depends on whether you are starting a new project or trying to convert an existing one. You can of course still use the "Basic" color management,but you will have to take into account the difference in input color values that I wrote before.

If "OpenColorIO" color management is used, you should note that you should always use the "Convert to OCIO..." button (even for new scenes), andin order to preserve render result for existing scenes, it is important to use the following color spaces when converting:

Note that using the "OpenColorIO" color management without converting the scene leaves it with the basic color inputs, but tries to use the OpenColorIO management for rendering which makes matching previous render result impossible to match.
You should also note that using the "OpenColorIO" will disable the "Color Management" option in the V-Ray settings, because the option will now be used from the OpenColorIO tab in the project settings (more details below).

So after the scene is converted, all color inputs in the scene (both in classic materials and shaders, as well as in node materials) will have the buttons in the color details to choose the exact color space in which to view the value of the color (left in the screenshot below).

While the render space used will be determined by the "Render Space" option in the document color management (right on the screenshot above) or simply use the "Preset" drop-down above. You should just note that currently V-Ray supports only the "ACEScg" and "scene-linear Rec.709-sRGB" as render color space.

2: When working in a AGX workflow what is the correct setup for Vray 6.1, mainly around color swatch issues?

About AGX - it is only a display transformation so it does not have direct relation to the actual rendering color space or inputs.

I hope this more or less answers your questions about how to use the color management with V-Ray.

[deyan.hadzhiev]

Hi seth_richardson I'll try to answer as extensively as I can.

3: When working in a sRGB/Linear Workflow what is the correct setup for Vray 6.1?

I'll start with a brief explanation of the state of working in sRGB/Linear Workflow as this is mostly applicable for older versions of Cinema 4D (R26 and older).

Disabling the "Linear Workflow" is not really supported, as V-Ray always uses Linear sRGB or ACEScg as a render color space internally.
The "Input Color Profile" option basically determines the color transformation that will be performed on classic materials and shader color inputs. When this option is "sRGB", an sRGB -> Linear transformation is performed, when it is "Linear" no transformation is performed on the colors. Note that this does not affect the node materials which are always storing and using linear values, but the color inputs there allow the values to be previewed either as linear or as sRGB, by this button in the expanded control:

So having covered the inputs, the color management in the V-Ray render settings only determines the render color space that is going to be used, but it is important to note that even if ACEScg is selected, the color inputs in the classic materials and shaders are considered in the color space determined by the "Input Color Profile".

1: When working in a ACES workflow what is the correct setup for Vray 6.1? I am assuming it is setting C4D Project settings to OCIO ACES.

It depends on your version of Cinema 4D. If you are using older Cinema 4D version (R26 and older) there is no much choice - there is only the "Basic" color management.
For 2023 it depends on whether you are starting a new project or trying to convert an existing one. You can of course still use the "Basic" color management,but you will have to take into account the difference in input color values that I wrote before.

If "OpenColorIO" color management is used, you should note that you should always use the "Convert to OCIO..." button (even for new scenes), andin order to preserve render result for existing scenes, it is important to use the following color spaces when converting:

Note that using the "OpenColorIO" color management without converting the scene leaves it with the basic color inputs, but tries to use the OpenColorIO management for rendering which makes matching previous render result impossible to match.
You should also note that using the "OpenColorIO" will disable the "Color Management" option in the V-Ray settings, because the option will now be used from the OpenColorIO tab in the project settings (more details below).

So after the scene is converted, all color inputs in the scene (both in classic materials and shaders, as well as in node materials) will have the buttons in the color details to choose the exact color space in which to view the value of the color (left in the screenshot below).

While the render space used will be determined by the "Render Space" option in the document color management (right on the screenshot above) or simply use the "Preset" drop-down above. You should just note that currently V-Ray supports only the "ACEScg" and "scene-linear Rec.709-sRGB" as render color space.

2: When working in a AGX workflow what is the correct setup for Vray 6.1, mainly around color swatch issues?

About AGX - it is only a display transformation so it does not have direct relation to the actual rendering color space or inputs.

I hope this more or less answers your questions about how to use the color management with V-Ray.

[seth_richardson]

I never replied to this but thank you for the very detailed answer. Is there something in the User Guide for this? If not I think this would be extremely helpful

[jeffrey_krigstein]

Hi Deyan, Thank you for your detailed response above. To be honest, I'm finding those instructions really difficult to get my head around (sorry!). I still don't have a clear understanding of how to set up a new scene correctly for ACES.

I've read through the User Guide page on ACEScg here, and it seems to say that the only thing we need to change is the V-Ray Render Settings' Color Management from sRGB to ACEScg and we're good to go. Does that mean there's no need to change the Project Settings or VFB settings at all?

If my understanding is correct, that doesn't seem to align with what you've said above about needing to change Color Management in Project Settings to OCIO and click Convert to OCIO even on new scenes.

Am I misunderstanding something or are some instructions newer than others?

Thanks for any guidance here.

Jeff

[akos_kiss]

Hi All!

Just wanted to chime in with the c4d ocio color management issues we're having We were interested in setting up the aces color management in c4d o that we could use the color picker to make matching brand colours for product visualization easier. For redshift this is an easier thing because if you switch the color picker to "Display" mode. It reverses the color management and it tris to match the colours to acescg. This is all well and good but with vray this doesn't seam to work.

I have to use the "Render" mode to get the same colour as i pick from an image. But if i use a node material and set the diffuse colour to "Render" mode and connect a color node it allways resets to "sRGB" mode after a while ( i don't know what triggers the reset) but if i change it to "Render" mode as i use with the classical material it still renders a bit different.

I'm just getting really confused. I would like to have a simple and easy way to pick and match brand colours in acescg. Is there a solution to this?

One bug I found that if you set up a vray material ( node or classic) with the project colour management set to aces. and change the self-illuminiation colour to anything from default. You can't turn of the self illumination it ignores the diffuse channel and just renders the "black" self illumination. It breaks the material.

I also just noticed that the node material self illumination channel doesn't have a brightness value like the classical material? Is this by design?