Designing a production pipeline with OCIO

The interest of OCIO* lies in the fact that by using it, you can configure the entire production chain in one go, for all the software in the pipeline (as long as they are compatible with OCIO).

In general, when configuring a production pipeline using OCIO, one starts from an existing configuration which is modified according to the needs of the project and artistic and technical choices.

A set of configurations is available in the OpenColorIO downloads, including ACES, spi-anim and spi-vfx, developed by Sony Pictures Imageworks. Another config is available with Blender.

Setting up

Setting up OCIO on a production pipeline is relatively simple. One must first choose a configuration to use, and possibly modify it and adapt it to one’s needs (see the following section Anatomy of an OCIO configuration).

The principle is then to give each application the path to the config.ocio configuration file. This can be done easily for all of them by modifying the OCIO environment variable (the exact manipulation depends on the operating system), giving it the path of the configuration file.

One can also generally give a specific path to each application; in this case the method varies depending on the application.

Anatomy of an OCIO configuration

An OCIO configuration actually consists of a set of LUTs* accompanied by a simple text file containing the actual configuration, always named config.ocio.

The config file is divided into several sections, generally in the following order:

Other sections can be added, see the official documentation for details on opencolorio.org.

Comments that do not affect the configuration can also be added to the file. A line containing a comment must simply begin with the character #.

Hint

The syntax actually follows the YAML standard.

We only explain here the different sections that a common user may need to modify, but all sections can be manipulated by more advanced users. You must then refer to the official OpenColorIO documentation.

Metadata

Example :

ocio_profile_version: 1
search_path: "luts:filmic"
strictparsing: true
luma: [0.2126, 0.7152, 0.0722]
description: RRT version ut33

Here is a description of some common parameters:

Roles

The roles section is the one that will be modified most often; it’s the one that defines how the different available color spaces are used, what the default spaces should be during the different production stages, etc.

(Commented) Example of Blender:

roles:
  reference: Linear
  # Internal scene linear space
  scene_linear: Linear
  rendering: Linear
  # Default color space for byte image
  default_byte: sRGB
  # Default color space for float images
  default_float: Linear
  # Default color space sequencer is working in
  default_sequencer: sRGB
  # Color spaces for color picking and texture painting (not internally supported yet)
  color_picking: sRGB
  texture_paint: Raw
  # Non-color data
  data: Non-Color
  # CIE XYZ color space
  XYZ: XYZ

On each line, the role is defined before the color space to be used. The name of the space must be that of one of the spaces available in the list in the following section.

ACES example:

roles:
  color_picking: Output - sRGB
  color_timing: ACES - ACEScc
  compositing_linear: ACES - ACEScg
  compositing_log: Input - ADX - ADX10
  data: Utility - Raw
  default: ACES - ACES2065-1
  matte_paint: Utility - sRGB - Texture
  reference: Utility - Raw
  rendering: ACES - ACEScg
  scene_linear: ACES - ACEScg
  texture_paint: ACES - ACEScc

Here are a few explanations about the different roles (alphabetical sorting):

Note

Not all applications will respect all roles: some may not be supported, or the application may not allow to change them (for example, Blender doesn’t allow to change its color picker space).

Some applications may also include other additional roles that aren’t listed here. This is the case for Blender with roles starting with default_ for example.

Displays

The displays section defines the list of different possible displays, for example work screens and screening room projectors.

Each display has a list of possible views, allowing to modify the display, for example for a technical validation, to better discern dark colors, etc.

Blender example:

displays:
  sRGB:
    - !<View> {name: Standard, colorspace: sRGB}
    - !<View> {name: Filmic, colorspace: Filmic sRGB}
    - !<View> {name: Filmic Log, colorspace: Filmic Log}
    - !<View> {name: Raw, colorspace: Raw}
    - !<View> {name: False Color, colorspace: False Color}
  XYZ:
    - !<View> {name: Standard, colorspace: XYZ}
    - !<View> {name: DCI, colorspace: dci_xyz}
    - !<View> {name: Raw, colorspace: Raw}
  None:
    - !<View> {name: Standard, colorspace: Raw}

The standard view displays sRGB values directly; Filmic Log can be used to check dark areas. Raw displays the data without conversion, for example to perform a technical check of a data layer (normal map, occlusion, etc.). False Color is also used for technical checks of the image.

ACES example:

displays:
  ACES:
    - !<View> {name: sRGB, colorspace: Output - sRGB}
    - !<View> {name: DCDM, colorspace: Output - DCDM}
    - !<View> {name: DCDM P3 gamut clip, colorspace: Output - DCDM (P3 gamut clip)}
    - !<View> {name: P3-D60, colorspace: Output - P3-D60}
    - !<View> {name: P3-D60 ST2084 1000 nits, colorspace: Output - P3-D60 ST2084 (1000 nits)}
    - !<View> {name: P3-D60 ST2084 2000 nits, colorspace: Output - P3-D60 ST2084 (2000 nits)}
    - !<View> {name: P3-D60 ST2084 4000 nits, colorspace: Output - P3-D60 ST2084 (4000 nits)}
    - !<View> {name: P3-DCI, colorspace: Output - P3-DCI}
    - !<View> {name: Rec.2020, colorspace: Output - Rec.2020}
    - !<View> {name: Rec.2020 ST2084 1000 nits, colorspace: Output - Rec.2020 ST2084 (1000 nits)}
    - !<View> {name: Rec.709, colorspace: Output - Rec.709}
    - !<View> {name: Rec.709 D60 sim., colorspace: Output - Rec.709 (D60 sim.)}
    - !<View> {name: sRGB D60 sim., colorspace: Output - sRGB (D60 sim.)}
    - !<View> {name: Raw, colorspace: Utility - Raw}
    - !<View> {name: Log, colorspace: Input - ADX - ADX10}

ACES doesn’t sort by different display types, and everything is gathered under one single display type.

Sources & References