Box2D integration module for Godot Engine

A simple C++ module integrating the Box2D physics library into Godot Engine. Development is still in very early stages, everything is untested.

• Godot: https://godotengine.org
• Box2D: http://box2d.org

Why?

Godot Engine already contains a very good, albeit simple, 2D physics engine implementation that is more than enough for most games. However, 2D games that require a bit more control and flexibility over its physics could benefit from a bigger and more complex implementation.

Features

• Integrates Box2D 3.1.2 into Godot as a C++ module.
• No setup required. If you can build Godot from source, you can use this module.
• Does not disable or replace Godot's 2D physics engine.
• Provides Object wrappers for every Box2D entity
  • i.e. b2World becomes WorldB2
• Full access from C++ and GDScript

Compilation

• Clone the contents of this repository into <Your Godot source folder>/modules/box2d
  • Please note that this project is meant to be used with Godot's 3.1 branch.
• Build and run Godot normally

How to use

This module attempts to mimick Box2D's API while remining faithful to Godot's naming standard. Remember that units are all in the KMS system.

Box2D API

GDScript

// Create world b2World world(b2Vec2(0.f, -10.f)); // Create a dynamic body b2BodyDef bodyDef; bodyDef.type = b2_dynamicBody; bodyDef.position.Set(0.f, 4.f); b2Body *body = world.CreateBody(&bodyDef); // Define a box b2PolygonShape dynamicBox; dynamicBox.SetAsBox(1.f, 1.f); // Attach the box to the dynamic body b2FixtureDef fixtureDef; fixtureDef.shape = &dynamicBox; fixtureDef.density = 1.f; body->CreateFixture(&fixtureDef); // Simulate world world.Step(1.f / 60.f, 6, 2);

# Create world var world = Box2D.world(Vector2(0, -10)) # Create a dynamic body var bodyDef = BodyDefB2.new() bodyDef.body_type = BodyB2.DYNAMIC bodyDef.position = Vector2(0, 4) var body = bodyDef.instance(world) # Define a box var dynamicBox = Box2D.box(Vector2(1, 1)) # Attach the box to the dynamic body var fixtureDef = FixtureDefB2.new() fixtureDef.shape = dynamicBox fixtureDef.density = 1 fixtureDef.instance(body) # Simulate world world.step(1 / 60, 6, 2)

Instead of the Create/Destroy combo (i.e. CreateJoint/DestroyJoint), Godot's familiar instance()/free() functions are used.

Box2D API	GDScript
// Create and destroy a body b2Body *body = world.CreateBody(&bodyDef); world.DestroyBody(body); // Create and destroy a joint b2Joint *joint = world.CreateJoint(&jointDef); world.DestroyJoint(joint);	# Create and destroy a body var body = bodyDef.instance(world) body.free() # Create and destroy a joint var joint = jointDef.instance(world) joint.free()

Same as Box2D's regular API, destroying a parent object automatically destroys its children.

Box2D API	GDScript
auto fixture = body->CreateFixture(&fixtureDef); world.DestroyBody(body); fixture->SetSensor(true); // ERROR	var fixture = fixtureDef.instance(body) body.free() fixture.set_sensor(true) # ERROR

The singleton Box2D provides functions for creating shapes and shortcuts for bodies and fixtures. (bypassing the need to create BodyDefB2 and FixtureDefB2)

# Shapes
shape = Box2D.box(Vector2(1, 1))
shape = Box2D.circle(Vector2(), 0.5)
# Shortcuts
body = Box2D.body(world, BodyB2.STATIC)
fixture = Box2D.fixture(body, shape, density)

This is all the documentation I have for this module, since it's in very early stages. If you know Box2D's API well enough, looking into the headers should point you in the right direction.

License

Released under the MIT License.