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This page provides information about the proper ACEScg color space workflow with V-Ray 5 for Maya.

 

Overview

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ACES is the Academy Color Encoding System and developed by the Academy of Motion Picture Arts and Sciences. ACEScg is the version of the ACES encoding system for computer graphics, widely adopted in the industry. It has become the industry standard, because compared to sRGB, ACEScg works with a lot more color information, illustrated in this gamut graph.

V-Ray 5 comes and V-Ray 6 come with an implementation of the ACEScg out of the box and in this tutorial we explain the rendering setup in V-Ray for Maya in this color space. There are two ways of setting up ACEScg for rendering and display: manually and using an OCIO configuration.

V-Ray supports only ACEScg as the primary color space of choice in CGI and not other ACES color spaces such as ACEScc or ACEScct.

See more information at the ACEScg courseware page.

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Manual Setup

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There are two ways to set V-Ray to render in ACEScg.

The recommended approach is to leave V-Ray’s color mapping to its default From Maya Preferences. This lets V-Ray follow Maya’s Color Management and the rules specified there, so you only need to specify ACEScg as the rendering color space in Maya.

Then, you can use the Color Management rules to automatically apply the input color space for your textures.

 

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Textures for bump mapping, normal mapping, displacement, etc. are usually encoded in linear sRGB andthey need to use the Raw color space in Maya. If you assign sRGB or any other color space for them in Maya's Color Management rules (or manually override the color space), they will produce wrong results.

It is recommended to assign a Raw color space for such texture with Color Management rules or manually.

 

 

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The new Frame Buffer in V-Ray 5 and later provides a filmic tonemap correction in AMPAS mode that emulates the OCIO display transformation, which can be used instead of an OCIO configuration.

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An automated OCIO configuration can be set with the OCIO environment variable.

There are a few steps you need to follow to set this up:

  1. Download the Open Color IO configuration package from GitHub: https://github.com/colour-science/OpenColorIO-Configs
  2. Set the OCIO environment variable and point it to the config.ocio file.
    For example, to set up the OCIO configuration with aces_1.0.32:
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Windows: set OCIO=C:\OpenColorIO-Configs\aces_1.0.32\config.ocio
 
Linux: export OCIO=/home/user/OpenColorIO-Configs/aces_1.0.32/config.ocio

macOS: export OCIO=/home/user/OpenColorIO-Configs/aces_1.0.32/config.ocio
See the Getting Started with Environment Variables page for more information.
3.  After launching Maya, enable Color Management and enable Use OCIO Configuration. You can then use the OCIO Input Color Space Rules or define custom rules within Maya Color Management.

 

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 4. When the VFB Display Correction is switched to OCIO, V-Ray reads the OCIO variable and loads the configuration there as well. Choose ACES - ACEScg for your Input Colorspace and sRGB for your View Transform. Leave the Display Device at ACES.

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The automated OCIO configuration can be further adjusted with the following VFB OCIO environment variables:

VRAY_VFB_OCIO – Automatically switches the OCIO button of the V-Ray VFB on.

VRAY_VFB_OCIO_INPUT_COLORSPACE – Specifies default OCIO input color space.

VRAY_VFB_OCIO_VIEW_TRANSFORM – Specifies default OCIO view transform.

For example, set a default OCIO input color space, display device, and view transform:

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Windows: set VRAY_VFB_OCIO = 1
Windows: set VRAY_VFB_OCIO_INPUT_COLORSPACE = ACES - ACEScg
Windows: set VRAY_VFB_OCIO_VIEW_TRANSFORM = sRGB

Linux: export VRAY_VFB_OCIO = 1 
Linux: export VRAY_VFB_OCIO_INPUT_COLORSPACE = ACES - ACEScg
Linux: export VRAY_VFB_OCIO_VIEW_TRANSFORM = sRGB

macOS: export VRAY_VFB_OCIO = 1
macOS: export VRAY_VFB_OCIO_INPUT_COLORSPACE = ACES - ACEScg
macOS: export VRAY_VFB_OCIO_VIEW_TRANSFORM = sRGB
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When rendering with V-Ray Standalone or using distributed rendering, the OCIO environment variables must be set accordingly on all other machines that are used for rendering. 

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The OCIO configuration files used in V-Ray VFB aren't automatically collected with the rest of the scene assets when sending a job for rendering to another machine. Use the OCIO configuration files from a shared location or copy the files manually to your render nodes to avoid mismatch in render output. 

See the Getting Started with Environment Variables page for more information.

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