OCIOLookTransform

OCIOLookTransform applies a creative colorspace transform using a predefined look in the OCIO config file. A look is a named color transform intended to modify the 'look' of an image in a creative way, rather than a technically or mathematically defined colorspace conversion. Examples of looks include a neutral grade applied to film scans prior to VFX work and per-shot digital intermediate (DI) grades required by the director's vision applied before a Viewer transform, such as rec1886.

OCIOLooks are predefined in OCIO config files before use and often reference per-shot or per-sequence LUTs or color corrections (CC). See https://opencolorio.org/ for more information on look configuration examples.

Note:  There are a number of NDK examples covering OCIO workflows that ship with the Nuke developer documentation, which can be found here:
<install_directory>/Documentation/NDKExamples/Plugins/00b_8source.html

Inputs and Controls

Connection Type

Connection Name

Function

Input

unnamed

The image sequence to receive the colorspace conversion.

mask

An optional image to use as a mask. By default, the colorspace conversion is limited to the non-black areas of the mask.

At first, the mask input appears as a triangle on the right side of the node, but when you drag it, it turns into an arrow labeled mask. If you cannot see the mask input, ensure that the mask control is disabled or set to none.

Control (UI)

Knob (Scripting)

Default Value

Function

OCIOLookTransform Tab

channels

channels

rgb

The colorspace conversion is applied only to these channels.

If you set this to something other than all or none, you can use the checkboxes on the right to select individual channels.

input

in_colorspace

scene_linear (linear)

Specifies the input colorspace.

Note:  The control label has been updated, but the knob name currently remains the same. The knob name will also change in a future release.

look

look

N/A

Specifies the look to apply as defined in the OCIO config file. You can specify a single look or multiple looks using the following syntax:

Multiple looks are combined with , (comma): 'a,b'

Direction is specified with +/- prefixes for forward and inverse: '+a, -b'

Missing look fallbacks are specified with | (pipe): 'a, -b, | -b'

Note:  ACES 1.3 OCIO configs include a Reference Gamut Compression look designed to correct wide gamut errors. This is the only look defined in the ACES 1.3 OCIO configs that ship with Nuke, so it is applied automatically. If more than one look is defined in the config, you can pick the look to apply using the look dropdown.

reload

reload

N/A

Click to reload all files used in the specified look(s).

invert direction

invert

disabled

Select invert direction to invert the transform.

output

out_colorspace

scene_linear (linear)

Specifies the output colorspace to which the input is converted.

Note:  The control label has been updated, but the knob name currently remains the same. The knob name will also change in a future release.

ignore errors

ignore_errors

disabled

When enabled, transforms that cannot locate a look defined in the OCIO config file are treated as a normal colorspace conversion from the input to the output colorspaces specified.

mask

N/A

disabled

Enables the associated mask channel to the right. Disabling this checkbox is the same as setting the channel to none.

maskChannelInput

none

The channel to use as a mask. By default, the colorspace conversion is limited to the non-black areas of this channel.

inject

inject

disabled

Copies the mask input to the predefined mask.a channel. Injecting the mask allows you to use the same mask further downstream.

invert

invert_mask

disabled

Inverts the use of the mask channel so that the colorspace conversion is limited to the non-white areas of the mask.

fringe

fringe

disabled

When enabled, only apply the effect to the edge of the mask.

When disabled, the effect is applied to the entire mask.

(un)premult by

N/A

disabled

Enables the associated channel to the right. Disabling this checkbox is the same as setting the channel to none.

unpremult

none

The image is divided by this channel before being processed, and multiplied again afterwards.

If you are using premultiplied input images, you may want to check (un)premult by and select rgba.alpha here. This will simulate doing the color conversion before the premultiplication was done. It is the same as adding an Unpremult node before this node and a Premult node after, but allows you to work faster if you’re only using one color correct node.

If you are using unpremultiplied input images, you should leave this set to none.

invert

invert_unpremult

disabled

Inverts the use of the (un)premultiply channel.

mix

mix

1

Dissolves between the original image at 0 and the full colorspace conversion at 1.

Context Tab

key1

key1

n/a

Allows you to add variables to register certain viewer processes by creating a custom config.ocio and specifying the variable in the to_reference file transform.

See Adding Context Viewer Processes for more information.

value1

value1

n/a

key2

key2

n/a

value2

value2

n/a

key3

key3

n/a

value3

value3

n/a

key4

key4

n/a

value4

value4

n/a