This page provides information about the proper ACEScg color space workflow with V-Ray 5 for Maya.
Overview
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 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.
Manual Setup
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.
Textures for bump mapping, normal mapping, displacement, etc. are usually encoded in linear sRGB and they 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.
If you have some files that are exceptions to the rule-based system, you can override the color space of a specific file node from its attributes.
For example, in the File texture, go to File Attributes > Color Space and select the color space, in which the texture is encoded.
Alternatively, you can instruct V-Ray to render directly in ACEScg.
Go to Render Settings > V-Ray > Color Mapping > Rendering color space and select ACEScg.
In all cases, in addition to bitmaps, V-Ray converts the light’s temperature settings, the V-Ray Sun & Sky, the VRayTemperature texture and the VRayMtl dispersion to the rendering color space.
Procedural colors are always treated as specified in the rendering color space by Maya, but displayed in your monitor’s color space in the interface.
This is another point in favor of using Maya’s Color Management system.
Textures for bump mapping, normal mapping, displacement, etc. are usually encoded in linear sRGB and they 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.
The new Frame Buffer in V-Ray 5 provides a filmic tonemap correction in AMPAS mode that emulates the OCIO display transformation, which can be used instead of an OCIO configuration.
OCIO configuration
An automated OCIO configuration can be set with the OCIO environment variable.
There are few steps you need to follow to set this up:
- Download the Open Color IO configuration package from GitHub: https://github.com/colour-science/OpenColorIO-Configs
- Set the OCIO environment variable and point it to the config.ocio file.
For example, to set up the OCIO configuration with aces_1.0.3:
Windows: set OCIO=C:\OpenColorIO-Configs\aces_1.0.3\config.ocio Linux: export OCIO=/home/user/OpenColorIO-Configs/aces_1.0.3/config.ocio macOS: export OCIO=/home/user/OpenColorIO-Configs/aces_1.0.3/config.ocio
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.
