A color manager is a connection between Arnold and an external color management library like OpenColorIO or synColor. Color managers hold information about the availability of different color spaces and also transform RGB colors to and from the rendering color space.

Default Color Manager

The default color manager implements the open-source OpenColorIO (OCIO) color management system and uses an OCIO v2 config shipped with Arnold. The color manager is configured to leverage the industry standard ACES color encoding system, setting the rendering color space to ACEScg.

Find more information on the ACES workflow here.

View Color Space

Viewer devices (e.g. monitor, TV screen, etc.) have limited dynamic range and color gamut. To display the rendered image properly on these devices, it has to be transformed to the viewing color space (usually Rec 709 for TV and sRGB for web).Besides the color transform, the image can also be tone mapped. Arnold uses the ACES 1.0 SDR-video view transform by default which offers filmic tone mapping.

Bake View Color Space Into Output

When rendering to the Picture Viewer or in Commandline or Team Viewer, Cinema 4D applies its native sRGB color transform, expecting the output to be in linear color space with sRGB primaries. That's not the case in Arnold when using a custom color manager (e.g. an ACES workflow with a custom view transform).

To get the correct output, this flag has to be set based on the image format we are targeting:

  • Turn on the flag when saving to an 8/16-bit integer image (e.g. JPEG, PNG, etc.).
  • Turn off the flag when saving to a 32-bit float image (e.g. EXR).

As opposed to the native workflow where you can save the rendered image from the Picture Viewer to any format, this flag must be set before rendering, defining the output format beforehand.

  • If the flag is turned on and saved to an EXR, the image will be incorrect, because Cinema 4D applies an sRGB -> linear transform, yet the image is in the View Color Space instead of sRGB.
  • If the flag is turned off and saved to a JPEG or PNG, the image will be incorrect, because Cinema 4D applies a linear -> sRGB transform, yet the image is in the Render Color Space (e.g. ACEScg) which is a wider gamut linear space.

Legacy Color Manager

This built-in color manager (the default color manager in Arnold 6) supports two color spaces:

  • 'sRGB' which corresponds to the sRGB colorspace with its corresponding gamma curve.
  • 'linear' which corresponds to a linear color space with the sRGB gamut and white point.

This color manager is equivalent to the native color management in Cinema 4D.

OCIO Color Manager

Through the 'color_manager_ocio' node Arnold can access color spaces defined in an OCIO config file. The color spaces are grouped by the families defined in the config file.

Config

A path to the OCIO config file to use, if this is empty OCIO will try to load the config file from the 'OCIO' environment variable.

sRGB color space (narrow)

If it exists in the OCIO config, this should be set to the name of the 'sRGB Gamma' color space. This is used internally for input and output color spaces in 'auto' mode. If set by the user, this color space is also used as a reference to detect the rendering color space gamut and white point.

Linear sRGB color space

This is the default color space used on linear input textures which uses sRGB primaries. Typically HDR (high dynamic range) images, e.g. skydome or area light textures.

Render color space (linear)

This is the default linear color space that Arnold will use as its rendering color space. Arnold's default color space is 'sRGB linear, ' but this can correspond to any linear color space if needed. If chromaticities for this linear color space can be guessed or are user-specified certain spectral effects will take them into account, but no other adaptations for albedos, transparencies, etc. are applied.

View Color Space

Viewer devices (e.g. monitor, TV screen, etc.) have limited dynamic range and color gamut. To display the rendered image properly on these devices, it has to be transformed to the viewing color space (usually Rec 709 for TV and sRGB for web).

Bake View Color Space Into Output

When rendering to the Picture Viewer or in Commandline or Team Viewer, Cinema 4D applies its native sRGB color transform, expecting the output to be in linear color space with sRGB primaries. That's not the case in Arnold when using a custom color manager (e.g. an ACES workflow with a custom view transform).

To get the correct output, this flag has to be set based on the image format we are targeting:

  • Turn on the flag when saving to an 8/16-bit integer image (e.g. JPEG, PNG, etc.).
  • Turn off the flag when saving to a 32-bit float image (e.g. EXR).

As opposed to the native workflow where you can save the rendered image from the Picture Viewer to any format, this flag must be set before rendering, defining the output format beforehand.

  • If the flag is turned on and saved to an EXR, the image will be incorrect, because Cinema 4D applies an sRGB -> linear transform, yet the image is in the View Color Space instead of sRGB.
  • If the flag is turned off and saved to a JPEG or PNG, the image will be incorrect, because Cinema 4D applies a linear -> sRGB transform, yet the image is in the Render Color Space (e.g. ACEScg) which is a wider gamut linear space.


  • No labels
© 2020-2021 Autodesk. All Rights Reserved / website terms / privacy/cookies / ccpa settings