BehaviorTree.CPP

Behavior Trees Library in C++. Batteries included.

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gdx-ai

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Artificial Intelligence framework for games based on libGDX or not. Features: Steering Behaviors, Formation Motion, Pathfinding, Behavior Trees and Finite State Machines

Quick Overview

BehaviorTree.CPP is a C++ library for creating and managing Behavior Trees, a popular technique in AI and robotics for designing complex, hierarchical behaviors. It offers a flexible framework for defining, composing, and executing behavior trees, with features like real-time visualization and XML-based tree definitions.

Pros

Highly modular and extensible architecture
Supports both synchronous and asynchronous node execution
Includes a graphical user interface for tree visualization and debugging
Provides XML-based tree definitions for easy serialization and deserialization

Cons

Steep learning curve for beginners unfamiliar with behavior trees
Limited documentation for advanced features
Requires C++11 or later, which may not be suitable for all projects
Performance overhead compared to hand-coded state machines for simple behaviors

Code Examples

Creating a simple behavior tree:

#include "behaviortree_cpp/bt_factory.h"

BT::BehaviorTreeFactory factory;
factory.registerNodeType<MyCustomNode>("CustomNode");

auto tree = factory.createTreeFromText(R"(
  <root main_tree_to_execute="MainTree">
    <BehaviorTree ID="MainTree">
      <Sequence name="root_sequence">
        <CustomNode />
        <SaySomething message="Hello, World!" />
      </Sequence>
    </BehaviorTree>
  </root>
)");

tree.tickRoot();

Implementing a custom action node:

#include "behaviortree_cpp/action_node.h"

class MyAction : public BT::SyncActionNode
{
public:
    MyAction(const std::string& name) : BT::SyncActionNode(name, {})
    {}

    BT::NodeStatus tick() override
    {
        std::cout << "MyAction: doing some work" << std::endl;
        return BT::NodeStatus::SUCCESS;
    }
};

Using blackboard to share data between nodes:

#include "behaviortree_cpp/blackboard.h"

BT::Blackboard::Ptr blackboard = BT::Blackboard::create();
blackboard->set("key", 42);

int value;
blackboard->get("key", value);
std::cout << "Value: " << value << std::endl;

Getting Started

Install the library using CMake:

git clone https://github.com/BehaviorTree/BehaviorTree.CPP.git
cd BehaviorTree.CPP
mkdir build && cd build
cmake ..
make
sudo make install

Include the library in your C++ project:

#include "behaviortree_cpp/bt_factory.h"

int main()
{
    BT::BehaviorTreeFactory factory;
    // Register your custom nodes and create your behavior tree here
    return 0;
}

Compile your project with the following flags:

g++ your_file.cpp -lbehaviortree_cpp -o your_program

Competitor Comparisons

gdx-ai

1,263

Artificial Intelligence framework for games based on libGDX or not. Features: Steering Behaviors, Formation Motion, Pathfinding, Behavior Trees and Finite State Machines

Pros of gdx-ai

Cross-platform support: Works with Java, Android, iOS, HTML5, and desktop platforms
Integrated with libGDX game development framework
Includes additional AI features like pathfinding and steering behaviors

Cons of gdx-ai

Limited to Java and languages that run on the JVM
May have a steeper learning curve for developers not familiar with libGDX
Less focused on behavior trees compared to BehaviorTree.CPP

Code Comparison

BehaviorTree.CPP:

BehaviorTreeFactory factory;
factory.registerSimpleCondition("BatteryOK", std::bind(CheckBattery));
factory.registerSimpleAction("SaySomething", std::bind(SaySomething, _1));

gdx-ai:

BehaviorTree<Dog> tree = new BehaviorTreeBuilder<>(dog)
    .sequence()
        .leaf("Bark", new BarkTask())
        .leaf("Walk", new WalkTask())
    .end()
    .build();

Both libraries provide ways to create behavior trees, but BehaviorTree.CPP uses a factory pattern with C++ bindings, while gdx-ai uses a builder pattern in Java. BehaviorTree.CPP offers more flexibility in registering custom actions and conditions, while gdx-ai integrates seamlessly with other libGDX components.

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README

License MIT

BehaviorTree.CPP 4.7

This C++ 17 library provides a framework to create BehaviorTrees. It was designed to be flexible, easy to use, reactive and fast.

Even if our main use-case is robotics, you can use this library to build AI for games, or to replace Finite State Machines.

There are few features which make BehaviorTree.CPP unique, when compared to other implementations:

It makes asynchronous Actions, i.e. non-blocking, a first-class citizen.
You can build reactive behaviors that execute multiple Actions concurrently (orthogonality).
Trees are defined using a Domain Specific scripting language (based on XML), and can be loaded at run-time; in other words, even if written in C++, the morphology of the Trees is not hard-coded.
You can statically link your custom TreeNodes or convert them into plugins and load them at run-time.
It provides a type-safe and flexible mechanism to do Dataflow between Nodes of the Tree.
It includes a logging/profiling infrastructure that allows the user to visualize, record, replay and analyze state transitions.

Documentation and Community

You can learn about the main concepts, the API and the tutorials here: https://www.behaviortree.dev/

An automatically generated API documentation can be found here: https://BehaviorTree.github.io/BehaviorTree.CPP/

If the documentation doesn't answer your questions and/or you want to connect with the other BT.CPP users, visit our forum

GUI Editor

Editing a BehaviorTree is as simple as editing an XML file in your favorite text editor.

If you are looking for a more fancy graphical user interface (and I know you do) check Groot2 out.

Groot screenshot

How to compile

BT.CPP requires a compile that supports c++17.

Three build systems are supported:

colcon (ament), if you use ROS2
conan otherwise (Linux/Windows).
straight cmake if you want to be personally responsible for dependencies :)

Compiling with conan:

Assuming that you are in the parent directory of BehaviorTree.CPP:

mkdir build_release
conan install . -of build_release -s build_type=Release
cmake -S . -B build_release -DCMAKE_TOOLCHAIN_FILE="build_release/conan_toolchain.cmake"
cmake --build build_release --parallel

If you have dependencies such as ZeroMQ and SQlite already installed and you don't want to use conan, simply type:

mkdir build_release
cmake -S . -B build_release
cmake --build build_release --parallel

If you want to build in a pixi project (conda virtual environment).

pixi run build

If you want to use BT.CPP in your application, please refer to the example here: https://github.com/BehaviorTree/btcpp_sample .

Commercial support

Are you using BT.CPP in your commercial product and do you need technical support / consulting? You can contact the primary author, dfaconti@aurynrobotics.com, to discuss your use case and needs.

Star History

Previous version

Version 3.8 of the software can be found in the branch v3.8.

That branch might receive bug fixes, but the new features will be implemented only in the master branch.

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Top Related Projects

gdx-ai

1,263

Artificial Intelligence framework for games based on libGDX or not. Features: Steering Behaviors, Formation Motion, Pathfinding, Behavior Trees and Finite State Machines

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