/aces-vwg-gamut-mapping-2020

ACES - Virtual Working Group - Gamut Mapping - 2020

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ACES - Virtual Working Group - Gamut Mapping - 2020

This repository hosts, in a version controlled location, a snapshot of the research and development effort of the ACES Virtual Working Group on Gamut Mapping - 2020.

The Virtual Working Group proposal can be read in this document.

A Dropbox Workspace is available as the central location for sharing resources.

Reference Implementations

In order to make the ACES 1.3 Reference Gamut Compression available prior to its wider native implementation in DCCs, a set of implementations in various forms is available in the reference folder of this repo.

These implementations are intended only as a stop-gap, and should be considered deprecated once the algorithm is either implemented natively in a particular DCC, or OCIO 2.1+ is supported.

Installation

    $ git clone https://github.com/colour-science/aces-vwg-gamut-mapping-2020.git
    $ cd aces-vwg-gamut-mapping-2020
    $ git submodule update --init --recursive

Model

The gamut mapping model selected by the Virtual Working Group is based on Smith (2020) - RGB Saturation Study Model.

The following implementations are available in the model directory:

Default Parameter Values

This Google Colab notebook shows calculations for the threshold values needed to protect the colors of the ColorChecker24, as defined in table D.1 of SMPTE 2065-1, and the distance limits needed to map the entirety of a set of common camera encoding gamuts into AP1.

Research

The research directory contains a mix of useful resources pertaining to research, experimentation and analysis conducted by the Virtual Working Group.

Extended ACES Configuration

To review the gamut mapping model objectively, the Virtual Working Group has extended the OpenColorIO ACES Configuration and added the following views:

  • ARRI ALF-2 (Rec.709)
  • ARRI K1S1 (Rec.709)
  • RED IPP2 (Rec.709)
  • Filmlight TCAM (Rec.709)

Because of its size, the complete configuration is only available from an external repository branch, however, the required LUTs and diff for the config.ocio file are archived and under version control in this repository along with the original Filmlight Baselight grade display rendering transforms.

Discussions pertaining to the configuration can be read in the dedicated thread.

Gamut Mapping Study Models

Smith (2020) - RGB Saturation Study Model

Smith (2020) - RGB Saturation Study Model is built on top of the RGB colourspace with the following approach:

  • An achromatic axis is computed for the scene-referred RGB exposure values.
  • The pseudo-distance between the individual 𝑅, 𝐺 and 𝐵 components and the achromatic axis is compressed with a cherry-picked compression function.

The model is extremely simple and elegant while offering good computational speed.

The following implementations are available:

Provides DCC implementation for :

Please refer to the repository README.md file for more information.

Collage Gamut Compressed

Resolve UI

Provides Python implementation via Jupyter Notebooks.

Please refer to the repository README.rst file for more information.

Gamut Medicina 05

Mansencal and Scharfenberg (2020) HSV Control Based Study Model

Mansencal and Scharfenberg (2020) HSV Control Based Study Model is built on top of the HSV colourspace with the following approach:

  • Scene-referred RGB exposure values are converted to HSV.
  • The saturation component 𝑆 is compressed with a cherry-picked compression function.
  • The hue component 𝐻 is warped according to user defined control values.
  • The HSV values are converted back to scene-referred RGB exposure values and then blended with the original scene-referred RGB exposure values function through a smoothstep function.

The model is much more complex and slower but offers direct controls over hue.

The following implementations are available:

Provides Python implementation via Jupyter Notebooks.

Please refer to the repository README.rst file for more information.

Gamut Medicina 01

Johnson (2020) ARRI Gamut Mapping Study Model

Johnson (2020) ARRI Gamut Mapping Study Model is focusing on ARRI colourspaces while adopting some principles from Smith (2020) model.

The following implementations are available:

Provides DCC implementation for The Foundry Nuke.

Please refer to the repository README.md file for more information.

Notebooks & Scripts

Simplistic Gamut Mapping Approaches in Nuke

A The Foundry Nuke script illustrating some examples of simplistic approaches to the gamut mapping problem by Matthias Scharfenberg.

Gamut Mapping Model as a 1D Shaper + 3D LUT

A The Foundry Nuke script showcasing how the gamut mapping model can be represented by a 1D Shaper + 3D LUT combination.

Gamut Mapper Equal Hue Line Comparison in Nuke

A The Foundry Nuke script comparing gamut mapped hue lines by Matthias Scharfenberg.

Sketches of Hue

A Jupyter Notebook exploring the concept of camera-referred "hue lines" by Sean Cooper.

Sketches of Hue

The notebook is directly viewable at this url and an online Google Colab implementation is also available.

Virtual Camera Primaries Rendering of Spectral Locus

An online Google Colab showcasing the distortions of camera spectral sensitivities upon projection in the CIE 1931 Chromaticity Diagram by Troy Sobotka.

Virtual Camera Primaries Rendering of Spectral Locus

The notebook is also archived and under version control in this repository.

colour-science Notebooks

An assortment of Google Colab notebooks produced for the Virtual Working Group.

The notebooks are also archived and under version control in this repository along with the DCP_Profiles_Data.json file generated by the DCP Profile Primaries & Distance Limits notebook.

Some notebooks have companion hosted pages:

License

For Third Party license details see THIRD_PARTY.

The ACES - Virtual Working Group - Gamut Mapping - 2020 Repository is provided by the Academy under the following terms and conditions:

Copyright © 2020 Academy of Motion Picture Arts and Sciences ("A.M.P.A.S."). Portions contributed by others as indicated. All rights reserved.

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Copies of source code, in whole or in part, must retain the above copyright notice, this list of conditions and the Disclaimer of Warranty.

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