II.F - Designing a production pipeline with OCIO¶

The interest of OCIO[](ZZ-vocabulaire.md) lies in the fact that, by using it, you can configure the entire production pipeline at once, for all the software in the pipeline (as long as they are compatible with OCIO*).

In general, when you configure a production pipeline using OCIO, you start with an existing config that you modify according to the needs of the project and the artistic and manufacturing choices.

A set of configurations is available in the [OpenColorIO] downloads (http://opencolorio.org), including ACES, spi-anim and spi-vfx, developed by Sony Pictures Imageworks. Another configuration is available with Blender.

F.1 - Setting up¶

The implementation of OCIO on a production pipeline is relatively simple. First of all, you have to choose a configuration to use, and eventually modify it and adapt it to your needs (see next section “OCIO config anatomy”).

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

It is also possible to give a specific path to each application; in this case the method varies according to the application.

F.2 - OCIO configuratin anatomy¶

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

Here is for example the Filmic config used by Blender:

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

• Metadata, including various information.
• Roles, defining in which cases which color spaces should be used.
• Displays, defining the spaces to be used for the display according to the screens.
• Colorspaces, containing the list of color spaces used.
• Looks (optional), containing the list of LUT and transformations that can be added to the image.

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 #.

We explain here only the different sections that a current user can modify, but all sections can be manipulated by more advanced users. You should refer to the official documentation of OpenColorIO.

F.2.a - 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:

• ocio_profile_version : either 1 or 2, depending on the version of OCIO to be used with this config.
• description (optional) : a brief description
• name (optional) : an unique name
• search_path (optional) : defines where the LUT needed for the config are. In this example, they are in two subfolders (separated by :): luts and filmic.
• luma (optional and discontinued) : old value used in particular by OCIO for the conversions in black and white of the colors. This value is actually no longer used anywhere, so it can be omitted. By default, it corresponds to the luminance of the Rec. 709 primaries.

F.2.b - Roles¶

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

Example (commented) 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, then 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 examples:

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 some explanations on the different roles (alphabetical sorting):

• color_picking : space for color selectors.
• color_timing : space for colorimetric corrections.
• compositing_linear : space for compositing.
• compositing_log : alternative space for some compositing operations.
• data : space for files (EXR) containing something other than color (normal maps, specs, etc.).
• matte_paint : space for images used in matte painting.
• reference : space used as a base for all the others ; the other spaces are defined according to this one.
• rendering : space to use for rendering.
• scene_linear : main working space : the one for 3D rendering in particular, the one for the generation of the image.
• texture_paint : similar to matte_paint but for textures used on 3D objects.

F.2.c - Displays¶

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

Example of Blender:

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.

Example of ACES:

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 does not sort by different displays, and everything is gathered under one display.

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Sources & References

• Documentation on OCIO configurations