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Introduction to behavior-tree

behavior-tree is a Go implementation of the behavior3 behavior tree. You can author logic nodes directly in the official online editor — the data format is kept identical to the original (it was translated from the JS version).

behavior-tree is the external repository and product brand for the Go module github.com/henrytien/behavior-tree. The Go package declaration is package behaviortree, not the hyphenated package behavior-tree; examples can continue to use b3 as an explicit import alias. This repository is derived from magicsea/behavior3go and is now maintained independently.

Naming policy​

  • Use behavior-tree for the external brand, repository name, documentation site, and module path.
  • Use behaviortree for the Go package declaration because Go identifiers cannot contain hyphens.
  • Documentation examples may continue to use b3 "github.com/henrytien/behavior-tree" to keep examples compact and compatible with behavior3-style constants.

How it differs from a typical behavior tree​

This behavior tree is a little different from the usual implementation:

  • Stateless structure: only a single copy of the tree structure is kept; all runtime state lives in the Blackboard.
  • A typical behavior tree needs one full tree per object to hold state. Here, a single tree instance can drive hundreds of objects, with each object's state isolated in its own blackboard.

This design is especially efficient for game servers that manage large numbers of AI entities.

Node categories​

A behavior tree is built from four kinds of nodes:

CategoryConstantDescription
CompositecompositeControls the execution order of children (Sequence / Priority, …)
DecoratordecoratorModifies the behavior of a single child (Inverter / Repeater, …)
ActionactionLeaf node that runs concrete logic (Wait / Log, …)
ConditionconditionLeaf node that returns a boolean-like result

Every Tick propagates a signal downward from the root. Each node returns one of four states: SUCCESS, FAILURE, RUNNING, ERROR.

Next steps​