🧩 Rigidbody2D

Built using the Box2d library.

The Rigidbody2D component provides a 2D physics body for a GameObject, enabling interaction with the physics simulation. It integrates the object into the Box2D world and controls physical properties such as density, friction, restitution, damping, and velocity.

A Rigidbody2D can be defined as dynamic, static, or kinematic, making it suitable for a wide range of use cases: characters, platforms, projectiles, sensors, or static colliders. Forces, impulses, and torques can be applied at runtime, and the component automatically keeps the associated GameObject’s transform in sync with the physics world.

Behaviour

The Rigidbody2D component integrates a GameObject into the 2D physics simulation. It automatically synchronizes the GameObject’s transform with the physics body, ensuring that position and rotation reflect the physics world. Forces, impulses, and torques applied through the component directly affect motion, velocity, and rotation. Changes to physical properties such as density, friction, restitution, or damping immediately influence how the body interacts with collisions and other Rigidbody2D instances. The body type (dynamic, static, kinematic) determines whether it responds to physics forces, is immovable, or can be controlled manually while still affecting other bodies.

Fields

• float density: Mass density of the body. Default is 10.0.

• float friction: Friction coefficient of the body. Default is 1.0.

• float restitution: Bounciness of the body. Default is 0.0.

• float restitutionThreshold: Minimum velocity required for restitution to take effect. Default is 0.0.

• BodyType bodyType: Type of body (static_body, dynamic_body, kinematic_body, or none_body).

• float radius: Radius of the body (if applicable).

• b2Body* body: Pointer to the Box2D body. Null if body hasn’t been created yet.

• b2Fixture* fixture: Pointer to the Box2D fixture associated with the body.

• ContactListenerPtr contactListener: Optional contact listener for collision callbacks.

• B2WorldPtr world: Reference to the physics world the body belongs to.

• ShapePtr shape: Shape used to create the body.

• Vector2 shapePos: Local position of the shape relative to the body.

Constructors

Default Constructor

Rigidbody2D()

Creates a new Rigidbody2D instance. No body is created until CreateBody is called.

Destructor

~Rigidbody2D()

Destroys the underlying physics body if it exists.

Body Management

CreateBody

void CreateBody(ShapePtr shape, BodyType bodyType = BodyType::dynamic_body, bool fixedRotation = false, MaskType maskType = MaskType::mask_1)

Creates and attaches a physics body to the component using the provided shape and parameters.

Parameters:

• shape: Shape of the body (rectangle, circle, polygon).

• bodyType: The type of body (dynamic, static, kinematic).

• fixedRotation: Whether the body should ignore rotation.

• maskType: Collision mask category.

DestroyBody

void DestroyBody()

Destroys the currently attached physics body, if any.

Physical Properties

Density

float GetDensity()
void SetDensity(float density)

Gets or sets the density of the body. Updating density recalculates the mass.

Friction

float GetFriction()
void SetFriction(float friction)

Gets or sets the surface friction coefficient.

Restitution

float GetRestitution()
void SetRestitution(float restitution)

Gets or sets the restitution (bounciness).

RestitutionThreshold

float GetRestitutionThreshold()
void SetRestitutionThreshold(float restitutionThreshold)

Gets or sets the minimum relative speed at which restitution is applied.

Inertia

float GetInertia()

Returns the rotational inertia of the body.

GravityScale

float GetGravityScale()

Returns the gravity scaling factor applied to this body.

Forces & Motion

ApplyForce

void ApplyForce(Vector2 force, bool wake = true)

Applies a continuous force to the body’s center.

ApplyLinearForce

void ApplyLinearForce(Vector2 force, bool wake = true)

Applies an instantaneous linear impulse to the body’s center.

ApplyAngularImpulse

void ApplyAngularImpulse(float impulse)

Applies an angular impulse, instantly changing angular velocity.

ApplyTorque

void ApplyTorque(float torque, bool wake = true)

Applies continuous torque to the body.

LinearVelocity

void SetLinearVelocity(Vector2 velocity)
Vector2 GetLinearVelocity()

Sets or gets the linear velocity.

SetVerticalVelocity

void SetVerticalVelocity(float vy)

Sets the vertical velocity, keeping horizontal unchanged.

SetHorizontalVelocity

void SetHorizontalVelocity(float vx)

Sets the horizontal velocity, keeping vertical unchanged.

SetAngularVelocity

void SetAngularVelocity(float va)

Sets the angular velocity.

SetAngularDamping

void SetAngularDamping(float ad)

Sets the angular damping factor (slows down rotation over time).

SetLinearDamping

void SetLinearDamping(float ld)

Sets the linear damping factor (slows down movement over time).

Transform & Orientation

Angle

float GetAngle()
void SetAngle(float angle)

Gets or sets the body’s rotation angle in radians.

GetPosition

Vector2 GetPosition()

Returns the current world position of the body.

SetPosition

void SetPosition(Vector2 position, bool awake = true)
void SetPosition(float x, float y, bool awake = true)

Moves the body to the given position.

SetRotation

void SetRotation(float angle, bool awake = true)

Rotates the body to the specified angle.

SetFixedRotation

void SetFixedRotation(bool flag)

Enables or disables rotation for the body.

Body Definition

BodyType

BodyType GetBodyType()
void SetBodyType(BodyType bodyType)

Gets or sets the type of the body (dynamic, static, kinematic).

GetShapeType

ShapeType GetShapeType()

Returns the type of the shape used by the body.

Tagging

Tag

void SetTag(String tag)
String GetTag()

Assigns or retrieves a string tag for the body, useful for categorization or identification.