Behavior Library

BehaviorLibrary is a framework for creating behavior trees for game AI. It is free to use, modify, and redestribute as covered under the attached License (FreeBSD).

Changes

RootSelector has been refactored to IndexSelector. It works exactly the same, just has a more appropriate name.

Behavior has had an additional constructor added that allows BehaviorComponent objects to be used rather than just RootSelector/IndexSelector objects.

Merged in new Repeater, Succeeder, RepeatUntilFail Decorators.

Utilities

Added Utility components, see Utility Test cases for test examples.

The basic point is to use a vector of floating numbers representing weights/values that will be paired with a BehaviorComponent object. When a UtilitySelector is called, it will execute a function that returns a UtilityVector that will then be compared against the BehaviorComponents' paired vectors (via a dot product) and select the pair that best matches and execute its Behavior.

Example

It is simple to use and with that simplicity comes performance.

Example of a simple A* following AI on a tilemap

//setup all coniditionals and their delegate functions
Conditional tooClose = new Conditional(isTooClose);
Conditional targetMoved = new Conditional(hasTargetMoved);
Conditional pathFound = new Conditional(hasPathBeenFound);
Conditional reachedCell = new Conditional(hasReachedCell);
Conditional reachedTarget = new Conditional(hasReachedTarget);
Conditional isNewPath = new Conditional(hasNewPath);

//setup all actions and their delegate functions
BehaviorAction moveToCell = new BehaviorAction(moveTowardsCell);
BehaviorAction calcPath = new BehaviorAction(calculatePath);
BehaviorAction initPathfinder = new BehaviorAction(initializePathfinder);
BehaviorAction getNextCell = new BehaviorAction(getNextPathCell);
BehaviorAction setPath = new BehaviorAction(setNewPath);
BehaviorAction getPath = new BehaviorAction(getCurrentPath);
BehaviorAction updatePosition = new BehaviorAction(updateTargetPosision);
BehaviorAction reset = new BehaviorAction(resetPathfinder);
BehaviorAction animate = new BehaviorAction(updateAnimation);

//setup an initilization branch
Sequence initialize = new Sequence(initPathfinder, calcPath);

//if the target has moved, reset and calculate a new path
Selector ifMovedCreateNewPath = new Selector(new Inverter(targetMoved), new Inverter(reset), calcPath);
Selector ifPathFoundGetPath = new Selector(new Inverter(pathFound), getPath);
Selector ifPathNewUseIt = new Selector(new Inverter(isNewPath), setPath);
Selector ifReachedCellGetNext = new Selector(new Inverter(reachedCell), getNextCell);
Selector ifNotReachedTargetMoveTowardsCell = new Selector(reachedTarget, moveToCell);
        
//follow target so long as you're not too close and then animate
Sequence follow = new Sequence(new Inverter(tooClose), updatePosition, ifMovedCreateNewPath, ifPathFoundGetPath, ifPathIsNewUseIt, ifReachedCellGetNext, ifNotReachedTargetMoveTowardsCell, animate);

//setup root node, choose initialization phase or pathing/movement phase
IndexSelector root = new IndexSelector(switchBehaviors, initialize, follow);

//set a reference to the root
Behavior behavior = new Behavior(root);

//to execute the behavior
behavior.Behave();