# Context Variables

## Global Context Variables

Global Context Variables are available to all nodes. Gaffer adds several of them by default, and you can also specify your own.

Global variables values can be edited in the interface’s Settings window (File > Settings…). Variables related to the script’s basic setup are assigned in the window’s Settings tab. Other global variables, including user-specified ones, can be added in the Variables tab. These settings can also be accessed from the ScriptNode object (for example, from the Python Editor: root["frameRange"] or root["variables"]["myVariable"]).

The default global Context Variables present in the graph root are:

Context Variable

Meaning

project:name

The name of the project the graph belongs to.

project:rootDirectory

The directory where the current graph’s project files are stored.

frame

The current frame of the graph.

framesPerSecond

The frame rate of the graph.

frameRange:start

The first frame in the frame range.

frameRange:end

The last frame in the frame range.

script:name

The name of the script.

## Built-in scene Context Variables

Gaffer can create the following built-in Context Variables inside scene Contexts:

Context Variable

Meaning

scene:path

Scene location being generated, when computing in service of a bound, transform, attributes, object, or childNames plug.

scene:setName

Name of the set being whose membership is being queried, when computing in service of a set plug.

scene:renderer

The active renderer during computation.

## Built-in image Context Variables

Gaffer can create the following built-in Context Variables inside image Contexts:

Context Variable

Meaning

image:tileOrigin

Coordinate of bottom-left pixel of tile being generated when computing in service of a channelData

image:channelName

Channel being generated when computing in service of a channelData

image:defaultFormat

The fallback format for image creation nodes, if no format has been specified.

## Node default Context Variables

Some nodes add additional Context Variables during execution. As such, these variables are only available upstream of these nodes in the graph. Most of them will have a plug that determines the Context Variable name(s). You can rename them as needed. The following table lists these default names.

Note

The prefix:name format in the default Context Variable names is merely a convention used to avoid clashes between variable names. We recommend you follow the same conventions when naming your own variables, but it is not compulsory.

Context Variable

Source node

Meaning

loop:index

Loop

Current iteration of the loop

wedge:value

Wedge

Value of the current wedge.

wedge:index

Wedge

Iteration of the current wedge.

collect:rootName

CollectScenes

Name of the current root location being added to the scene.

collect:layerName

CollectImages

Name of the current layer being added to the image.

## Accessing Context Variables

For the available methods to access Context Variables with the Python and OSL APIs, see the Expressions reference.

Note

To query plug values in the API, you must first instantiate an appropriate Context object. See Contexts and Common Operations for more details.