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["framRange"] or root["variables"]["myVariable"]).

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

Global 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:

Build-in scene 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:

Build-in image Context Variable Meaning
image:tileOrigin Coordinate of bottom-left pixel of tile being generated when computing in service of a channelData plug.
image:channelName Channel being generated when computing in service of a channelData plug.
image:defaultFormat The fallback format of an image network, if no format has been specified. A GafferImage.FormatData object. Use the value property to get the GafferImage.Format.

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.


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.


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