A revolute joint allows for relative rotation in the 2D plane with no relative translation. More...

Collaboration diagram for Revolute Joint:

Data Structures
struct	b2RevoluteJointDef
	Revolute joint definition. More...

Functions
B2_API b2JointId	b2CreateRevoluteJoint (b2WorldId worldId, const b2RevoluteJointDef *def)
	Create a revolute joint.

B2_API void	b2RevoluteJoint_EnableSpring (b2JointId jointId, bool enableSpring)
	Enable/disable the revolute joint spring.

B2_API bool	b2RevoluteJoint_IsSpringEnabled (b2JointId jointId)
	It the revolute angular spring enabled?

B2_API void	b2RevoluteJoint_SetSpringHertz (b2JointId jointId, float hertz)
	Set the revolute joint spring stiffness in Hertz.

B2_API float	b2RevoluteJoint_GetSpringHertz (b2JointId jointId)
	Get the revolute joint spring stiffness in Hertz.

B2_API void	b2RevoluteJoint_SetSpringDampingRatio (b2JointId jointId, float dampingRatio)
	Set the revolute joint spring damping ratio, non-dimensional.

B2_API float	b2RevoluteJoint_GetSpringDampingRatio (b2JointId jointId)
	Get the revolute joint spring damping ratio, non-dimensional.

B2_API float	b2RevoluteJoint_GetAngle (b2JointId jointId)
	Get the revolute joint current angle in radians relative to the reference angle.

B2_API void	b2RevoluteJoint_EnableLimit (b2JointId jointId, bool enableLimit)
	Enable/disable the revolute joint limit.

B2_API bool	b2RevoluteJoint_IsLimitEnabled (b2JointId jointId)
	Is the revolute joint limit enabled?

B2_API float	b2RevoluteJoint_GetLowerLimit (b2JointId jointId)
	Get the revolute joint lower limit in radians.

B2_API float	b2RevoluteJoint_GetUpperLimit (b2JointId jointId)
	Get the revolute joint upper limit in radians.

B2_API void	b2RevoluteJoint_SetLimits (b2JointId jointId, float lower, float upper)
	Set the revolute joint limits in radians.

B2_API void	b2RevoluteJoint_EnableMotor (b2JointId jointId, bool enableMotor)
	Enable/disable a revolute joint motor.

B2_API bool	b2RevoluteJoint_IsMotorEnabled (b2JointId jointId)
	Is the revolute joint motor enabled?

B2_API void	b2RevoluteJoint_SetMotorSpeed (b2JointId jointId, float motorSpeed)
	Set the revolute joint motor speed in radians per second.

B2_API float	b2RevoluteJoint_GetMotorSpeed (b2JointId jointId)
	Get the revolute joint motor speed in radians per second.

B2_API float	b2RevoluteJoint_GetMotorTorque (b2JointId jointId)
	Get the revolute joint current motor torque, usually in newton-meters.

B2_API void	b2RevoluteJoint_SetMaxMotorTorque (b2JointId jointId, float torque)
	Set the revolute joint maximum motor torque, usually in newton-meters.

B2_API float	b2RevoluteJoint_GetMaxMotorTorque (b2JointId jointId)
	Get the revolute joint maximum motor torque, usually in newton-meters.

b2RevoluteJointDef	b2DefaultRevoluteJointDef (void)
	Use this to initialize your joint definition.

Detailed Description

A revolute joint allows for relative rotation in the 2D plane with no relative translation.

The revolute joint is probably the most common joint. It can be used for ragdolls and chains. Also called a hinge or pin joint.

Data Structure Documentation

◆ b2RevoluteJointDef

struct b2RevoluteJointDef

Revolute joint definition.

This requires defining an anchor point where the bodies are joined. The definition uses local anchor points so that the initial configuration can violate the constraint slightly. You also need to specify the initial relative angle for joint limits. This helps when saving and loading a game. The local anchor points 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

Collaboration diagram for b2RevoluteJointDef:

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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	dampingRatio	The spring damping ratio, non-dimensional.
float	drawSize	Scale the debug draw.
bool	enableLimit	A flag to enable joint limits.
bool	enableMotor	A flag to enable the joint motor.
bool	enableSpring	Enable a rotational spring on the revolute hinge axis.
float	hertz	The spring stiffness Hertz, cycles per second.
int	internalValue	Used internally to detect a valid definition. DO NOT SET.
b2Vec2	localAnchorA	The local anchor point relative to bodyA's origin.
b2Vec2	localAnchorB	The local anchor point relative to bodyB's origin.
float	lowerAngle	The lower angle for the joint limit in radians. Minimum of -0.95*pi radians.
float	maxMotorTorque	The maximum motor torque, typically in newton-meters.
float	motorSpeed	The desired motor speed in radians per second.
float	referenceAngle	The bodyB angle minus bodyA angle in the reference state (radians). This defines the zero angle for the joint limit.
float	upperAngle	The upper angle for the joint limit in radians. Maximum of 0.95*pi radians.
void *	userData	User data pointer.

Function Documentation

◆ b2CreateRevoluteJoint()

B2_API b2JointId b2CreateRevoluteJoint	(	b2WorldId	worldId,
		const b2RevoluteJointDef *	def )

Create a revolute joint.

See also: b2RevoluteJointDef for details

◆ b2RevoluteJoint_GetAngle()

B2_API float b2RevoluteJoint_GetAngle ( b2JointId jointId )

Get the revolute joint current angle in radians relative to the reference angle.

See also: b2RevoluteJointDef::referenceAngle

◆ b2RevoluteJoint_SetLimits()

B2_API void b2RevoluteJoint_SetLimits	(	b2JointId	jointId,
		float	lower,
		float	upper )

Set the revolute joint limits in radians.

It is expected that lower <= upper and that -0.95 * B2_PI <= lower && upper <= -0.95 * B2_PI.

Data Structures