Behaviour Tree Visualizer

Behaviour trees have become the standard way to structure robot decision making in ROS 2: Nav2 uses them for navigation, and BehaviorTree.CPP powers trees on robots of every kind. Their XML is easy for machines and hard for people. The Behaviour Tree Visualizer turns that XML into a picture and checks it for the mistakes that stop it from loading.

What it does

• Draws BehaviorTree.CPP 3 and 4 XML, including Groot files and Nav2 trees, left to right or top down.
• Colours nodes by type: controls, decorators, actions, conditions and subtrees.
• Checks the structure: one root node per tree, existing subtrees, no subtree loops, exactly one child per decorator, no children on leaves, and the child counts of nodes such as IfThenElse and Switch.
• Knows every built-in node of BehaviorTree.CPP 4.10 and the Nav2 nodes in ROS 2 Jazzy, and flags version 3 names.
• Exports the drawing as SVG.

How it is checked

We load the same sample files with BehaviorTree.CPP 4.10 itself and compare: trees the visualizer calls valid load, and the deliberately broken sample is rejected for the same reason the visualizer reports first.

Running trees for real

The visualizer reads trees. To design trees together and run them on a fleet of robots, XPARO's fleet dashboard includes a collaborative behaviour tree editor and engine.

Open the Behaviour Tree Visualizer. The guides below introduce behaviour trees, explain the XML format, compare trees with state machines, collect proven design patterns, and walk through Nav2's own tree.