Context, Fields and Attributes

geometry nodes
Author

ozm

Published

August 28, 2025

Context, Fields and Attributes are the most fundamental concepts in Geometry Nodes.

The documentation on fields is worth a read. But here is a quick, very simplified and maybe not 100% correct run down:

There are two types of nodes: Data Flow and Field nodes.
We can generalize, that Data Flow nodes have Geometry Inputs. All others can be considered Field nodes:
Two node types. Data Flow have Geo Inputs and Outputs. All others are Field nodes

A group of Field nodes can be thought of like a function in programming:
they describe functionality, they take inputs and they can be reused in many places.
Field Nodes form a Function. In Programming, a func can be used over and over, with DIFFERENT DATA

Field nodes take their input data from the Data Flow nodes they are connected to (!). So, in the node tree, the data we pass to our function (group of Field nodes) does not come from the left, but from the right! The Data Flow nodes defines the Context in which the Field nodes are evaluated in:
The data for the function comes from the DATA FLOW node. The DATA FLOW node sets the CONTEXT in which the group of Field nodes are evaluated

This means, we can reuse our Field nodes and they will output different data, depending on the Data Flow nodes they are connected to (the Context):
Here, the function is reused on two different DATA FLOW nodes, in two different contexts. The POSITION node will output the position data defined by the context.

Same situation here:
Same thing here, the POSITION node will output different values, because of context

Here, we save an Attribute on the data. We access this data in the Field nodes. Only if the attribute is available in the context, the data will be returned:
Adding Attributes to the DATA FLOW and accessing the attribute in fields. RANDOM is evaluated on each point of the geometry using the ID. This is different in each geometry

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