BrainTree
                                
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                        C++ behavior tree single header library
BrainTree
A C++ behavior tree single header library.
Features
- behavior tree implementation
- predefined composites
- predefined decorators
- (optional) rudimentary blackboard
- (optional) behavior tree builders
Install
Include BrainTree.h in your project.
Example
// this example should print out "Hello, World!", four times
#include <iostream>
#include "BrainTree.h"
class Action : public BrainTree::Node
{
public:
    Status update() override
    {
        std::cout << "Hello, World!" << std::endl;
        return Node::Status::Success;
    }
};
void CreatingBehaviorTreeManually()
{
    BrainTree::BehaviorTree tree;
    auto sequence = std::make_shared<BrainTree::Sequence>();
    auto sayHello = std::make_shared<Action>();
    auto sayHelloAgain = std::make_shared<Action>();
    sequence->addChild(sayHello);
    sequence->addChild(sayHelloAgain);
    tree.setRoot(sequence);
    tree.update();
}
void CreatingBehaviorTreeUsingBuilders()
{
    auto tree = BrainTree::Builder()
        .composite<BrainTree::Sequence>()
            .leaf<Action>()
            .leaf<Action>()
        .end()
        .build();
    tree->update();
}
int main()
{
    CreatingBehaviorTreeManually();
    CreatingBehaviorTreeUsingBuilders();
    return 0;
}
Composites
Selector
- The Selector composite ticks each child node in order.
- If a child succeeds or runs, the selector returns the same status.
- In the next tick, it will try to run each child in order again.
- If all children fails, only then does the selector fail.
Sequence
- The Sequence composite ticks each child node in order.
- If a child fails or runs, the sequence returns the same status.
- In the next tick, it will try to run each child in order again.
- If all children succeeds, only then does the sequence succeed.
StatefulSelector
- The StatefulSelector composite ticks each child node in order, and remembers what child it prevously tried to tick.
- If a child succeeds or runs, the stateful selector returns the same status.
- In the next tick, it will try to run the next child or start from the beginning again.
- If all children fails, only then does the stateful selector fail.
StatefulSequence
- The StatefulSequence composite ticks each child node in order, and remembers what child it prevously tried to tick.
- If a child fails or runs, the stateful sequence returns the same status.
- In the next tick, it will try to run the next child or start from the beginning again.
- If all children succeeds, only then does the stateful sequence succeed.
Builder
The Builder class simplifies the process of creating a behavior tree. You use three methods to build your tree:
- leaf<NodeType>()
- composite<CompositeType>()
- decorator<DecoratorType>()
Both composite() and decorator() require a corresponding call to end(), this marks where you are done adding children to a composite or a child to a decorator. At the very end you call build() which will then give you the finished behavior tree.
auto tree = Builder()
    .decorator<Repeater>()
        .composite<Sequence>()
            .leaf<SayHello>("Foo")
            .leaf<SayHello>("Bar")
        .end()
    .end()
    .build();
License
MIT (c) Pär Arvidsson 2015-2018