Joints allow you to connect rigid bodies together while allowing various forms of relative motion. More...

Topics
	Distance Joint
	Functions for the distance joint.
	Filter Joint
	Functions for the filter joint.
	Motor Joint
	Functions for the motor joint.
	Mover Joint
	Functions for the mover joint.
	Pogo Joint
	Functions for the pogo joint.
	Prismatic Joint
	A prismatic joint allows for translation along a single axis with no rotation.
	Revolute Joint
	A revolute joint allows for relative rotation in the 2D plane with no relative translation.
	Weld Joint
	A weld joint fully constrains the relative transform between two bodies while allowing for springiness.
	Wheel Joint
	The wheel joint can be used to simulate wheels on vehicles.

Data Structures
struct	b2JointDef
	Base joint definition used by all joint types. More...

Enumerations
enum	b2JointType
	Joint type enumeration. More...

Functions
void	b2DestroyJoint (b2JointId jointId)
	Destroy a joint.
bool	b2Joint_IsValid (b2JointId id)
	Joint identifier validation. Provides validation for up to 64K allocations.
b2JointType	b2Joint_GetType (b2JointId jointId)
	Get the joint type.
b2BodyId	b2Joint_GetBodyA (b2JointId jointId)
	Get body A id on a joint.
b2BodyId	b2Joint_GetBodyB (b2JointId jointId)
	Get body B id on a joint.
b2WorldId	b2Joint_GetWorld (b2JointId jointId)
	Get the world that owns this joint.
void	b2Joint_SetLocalFrameA (b2JointId jointId, b2Transform localFrame)
	Set the local frame on bodyA.
b2Transform	b2Joint_GetLocalFrameA (b2JointId jointId)
	Get the local frame on bodyA.
void	b2Joint_SetLocalFrameB (b2JointId jointId, b2Transform localFrame)
	Set the local frame on bodyB.
b2Transform	b2Joint_GetLocalFrameB (b2JointId jointId)
	Get the local frame on bodyB.
void	b2Joint_SetCollideConnected (b2JointId jointId, bool shouldCollide)
	Toggle collision between connected bodies.
bool	b2Joint_GetCollideConnected (b2JointId jointId)
	Is collision allowed between connected bodies?
void	b2Joint_SetUserData (b2JointId jointId, void *userData)
	Set the user data on a joint.
void *	b2Joint_GetUserData (b2JointId jointId)
	Get the user data on a joint.
void	b2Joint_WakeBodies (b2JointId jointId)
	Wake the bodies connected to this joint.
b2Vec2	b2Joint_GetConstraintForce (b2JointId jointId)
	Get the current constraint force for this joint. Usually in Newtons.
float	b2Joint_GetConstraintTorque (b2JointId jointId)
	Get the current constraint torque for this joint. Usually in Newton * meters.
float	b2Joint_GetLinearSeparation (b2JointId jointId)
	Get the current linear separation error for this joint.
float	b2Joint_GetAngularSeparation (b2JointId jointId)
	Get the current angular separation error for this joint.
void	b2Joint_SetConstraintTuning (b2JointId jointId, float hertz, float dampingRatio)
	Set the joint constraint tuning.
void	b2Joint_GetConstraintTuning (b2JointId jointId, float hertz, float dampingRatio)
	Get the joint constraint tuning. Advanced feature.
void	b2Joint_SetForceThreshold (b2JointId jointId, float threshold)
	Set the force threshold for joint events (Newtons).
float	b2Joint_GetForceThreshold (b2JointId jointId)
	Get the force threshold for joint events (Newtons).
void	b2Joint_SetTorqueThreshold (b2JointId jointId, float threshold)
	Set the torque threshold for joint events (N-m).
float	b2Joint_GetTorqueThreshold (b2JointId jointId)
	Get the torque threshold for joint events (N-m).

Detailed Description

Joints allow you to connect rigid bodies together while allowing various forms of relative motion.

Data Structure Documentation

◆ b2JointDef

struct b2JointDef

Base joint definition used by all joint types.

The local frames are measured from the body's origin rather than the center of mass because:

you might not know where the center of mass will be.
if you add/remove shapes from a body and recompute the mass, the joints will be broken.

Data Fields
b2BodyId	bodyIdA	The first attached body.
b2BodyId	bodyIdB	The second attached body.
bool	collideConnected	Set this flag to true if the attached bodies should collide.
float	constraintDampingRatio	Constraint damping ratio (advanced feature).
float	constraintHertz	Constraint hertz (advanced feature).
float	drawScale	Debug draw scale.
float	forceThreshold	Force threshold for joint events.
b2Transform	localFrameA	The first local joint frame.
b2Transform	localFrameB	The second local joint frame.
float	torqueThreshold	Torque threshold for joint events.
void *	userData	User data pointer.

Enumeration Type Documentation

◆ b2JointType

enum b2JointType

Joint type enumeration.

This is useful because all joint types use b2JointId and sometimes you want to get the type of a joint.

Enumerator
b2_distanceJoint	constrain the distance between two points
b2_filterJoint	filter collision between two bodies
b2_motorJoint	fully control the movement of a body
b2_moverJoint	control the movement of the dynamic character mover
b2_pogoJoint	ground interaction for the dynamic character mover
b2_prismaticJoint	slide along an axis
b2_revoluteJoint	rotate around a pivot
b2_weldJoint	bring two bodies together with some flex
b2_wheelJoint	wheel spins with shock absorber

Function Documentation

◆ b2Joint_GetAngularSeparation()

float b2Joint_GetAngularSeparation ( b2JointId jointId )

Get the current angular separation error for this joint.

Does not consider admissible movement. Radians.

◆ b2Joint_GetLinearSeparation()

float b2Joint_GetLinearSeparation ( b2JointId jointId )

Get the current linear separation error for this joint.

Does not consider admissible movement. Usually in meters.

◆ b2Joint_SetConstraintTuning()

void b2Joint_SetConstraintTuning	(	b2JointId	jointId,
		float	hertz,
		float	dampingRatio )

Set the joint constraint tuning.

Advanced feature.

Parameters

jointId	the joint
hertz	the stiffness in Hertz (cycles per second)
dampingRatio	the non-dimensional damping ratio (one for critical damping)

Topics

Data Structures

Enumerations

Functions