Module org.dyn4j
Package org.dyn4j.dynamics.joint

Class AngleJoint<T extends PhysicsBody>

  • Type Parameters:
    T - the PhysicsBody type
    All Implemented Interfaces:
    DataContainer, AngularLimitsJoint, Joint<T>, PairedBodyJoint<T>, Shiftable, Ownable
    public class AngleJoint<T extends PhysicsBody>
extends AbstractPairedBodyJoint<T>
implements AngularLimitsJoint, PairedBodyJoint<T>, Joint<T>, Shiftable, DataContainer, Ownable
    Implementation of an angle joint.

    A angle joint constrains the relative rotation of two bodies. The bodies will continue to translate freely.

    By default the lower and upper limit angles are set to the current angle between the bodies. When the lower and upper limits are equal, the bodies rotate together and are not allowed rotate relative to one another. By default the limits are enabled.

    If the lower and upper limits are set explicitly, the values must follow these restrictions:

    • lower limit ≤ upper limit
    • lower limit > -180
    • upper limit < 180
    To create a joint with limits outside of this range use the setLimitsReferenceAngle(double) method. This method sets the baseline angle for the joint, which represents 0 radians in the context of the limits. For example: 
     // we would like the joint limits to be [30, 260]
 // this is the same as the limits [-60, 170] if the reference angle is 90
 joint.setLimits(Math.toRadians(-60), Math.toRadians(170));
 joint.setReferenceAngle(Math.toRadians(90));
    The angle joint also allows a ratio value that allow the bodies to rotate at a specified value relative to the other. This can be used to simulate gears.

    Since the AngleJoint class defaults the upper and lower limits to the same value and by default the limits are enabled, you will need to disable the limit to see the effect of the ratio.

    Since:
    2.2.2
    Version:
    5.0.0
    Author:
    William Bittle
    See Also:
    Documentation, Angle Constraint

    • Field Detail

      • ratio

        protected double ratio
        The angular velocity ratio

      • lowerLimit

        protected double lowerLimit
        The lower limit

      • upperLimit

        protected double upperLimit
        The upper limit

      • limitsEnabled

        protected boolean limitsEnabled
        Whether the limits are enabled

      • referenceAngle

        protected double referenceAngle
        The initial angle between the two bodies

    • Method Detail

      • initializeConstraints

        public void initializeConstraints​(TimeStep step,
                                  Settings settings)
        Description copied from interface: Joint
        Performs any initialization of the velocity and position constraints.
        Specified by:
        initializeConstraints in interface Joint<T extends PhysicsBody>
        Parameters:
        step - the time step information
        settings - the current world settings

      • solveVelocityConstraints

        public void solveVelocityConstraints​(TimeStep step,
                                     Settings settings)
        Description copied from interface: Joint
        Solves the velocity constraints.
        Specified by:
        solveVelocityConstraints in interface Joint<T extends PhysicsBody>
        Parameters:
        step - the time step information
        settings - the current world settings

      • solvePositionConstraints

        public boolean solvePositionConstraints​(TimeStep step,
                                        Settings settings)
        Description copied from interface: Joint
        Solves the position constraints.
        Specified by:
        solvePositionConstraints in interface Joint<T extends PhysicsBody>
        Parameters:
        step - the time step information
        settings - the current world settings
        Returns:
        boolean true if the position constraints were solved

      • getReactionForce

        public Vector2 getReactionForce​(double invdt)
        Returns the force applied to the PhysicsBodys in order to satisfy the constraint in newtons.

        Not applicable to this joint. Returns a new zero Vector2.

        Specified by:
        getReactionForce in interface Joint<T extends PhysicsBody>
        Parameters:
        invdt - the inverse delta time
        Returns:
        Vector2

      • getReactionTorque

        public double getReactionTorque​(double invdt)
        Description copied from interface: Joint
        Returns the torque applied to the PhysicsBodys in order to satisfy the constraint in newton-meters.
        Specified by:
        getReactionTorque in interface Joint<T extends PhysicsBody>
        Parameters:
        invdt - the inverse delta time
        Returns:
        double

      • shift

        public void shift​(Vector2 shift)
        Description copied from interface: Shiftable
        Translates the object to match the given coordinate shift.
        Specified by:
        shift in interface Shiftable
        Parameters:
        shift - the amount to shift along the x and y axes

      • getJointAngle

        public double getJointAngle()
        Returns the relative angle between the two PhysicsBodys in radians in the range [-π, π].
        Returns:
        double
        Since:
        3.1.0

      • getRatio

        public double getRatio()
        Returns the angular velocity ratio between the two bodies.
        Returns:
        double
        Since:
        3.1.0

      • setRatio

        public void setRatio​(double ratio)
        Sets the angular velocity ratio between the two bodies.

        A value of 0.5 means that body1 will rotate 2 times while body2 rotates once. A value of 2 means that body2 will rotate 2 times while body1 rotates once.

        A value of 1.0 means that the body rotate at the same rate.

        A negative ratio indicates that the anglular velocities of the joined bodies should be in opposite directions.

        A ratio of zero is not supported.

        Parameters:
        ratio - the ratio; anything, just not zero
        Throws:
        IllegalArgumentException - if ratio is equal to zero
        Since:
        3.1.0

      • setLimitsEnabled

        public void setLimitsEnabled​(boolean flag)
        Description copied from interface: AngularLimitsJoint
        Enables or disables the angular limits.
        Specified by:
        setLimitsEnabled in interface AngularLimitsJoint
        Parameters:
        flag - true if the limit should be enabled

      • setUpperLimit

        public void setUpperLimit​(double upperLimit)
        Description copied from interface: AngularLimitsJoint
        Sets the upper angular limit.

        Must be greater than or equal to the lower angular limit.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setUpperLimit in interface AngularLimitsJoint
        Parameters:
        upperLimit - the upper angular limit in radians

      • setLowerLimit

        public void setLowerLimit​(double lowerLimit)
        Description copied from interface: AngularLimitsJoint
        Sets the lower angular limit.

        Must be less than or equal to the upper angular limit.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setLowerLimit in interface AngularLimitsJoint
        Parameters:
        lowerLimit - the lower angular limit in radians

      • setLimits

        public void setLimits​(double lowerLimit,
                      double upperLimit)
        Description copied from interface: AngularLimitsJoint
        Sets the upper and lower angular limits.

        The lower limit must be less than or equal to the upper limit.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setLimits in interface AngularLimitsJoint
        Parameters:
        lowerLimit - the lower limit in radians
        upperLimit - the upper limit in radians

      • setLimitsEnabled

        public void setLimitsEnabled​(double lowerLimit,
                             double upperLimit)
        Description copied from interface: AngularLimitsJoint
        Sets both the lower and upper limits and enables them.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setLimitsEnabled in interface AngularLimitsJoint
        Parameters:
        lowerLimit - the lower limit in radians
        upperLimit - the upper limit in radians

      • setLimits

        public void setLimits​(double limit)
        Description copied from interface: AngularLimitsJoint
        Sets both the lower and upper limits to the given limit.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setLimits in interface AngularLimitsJoint
        Parameters:
        limit - the desired limit

      • setLimitsEnabled

        public void setLimitsEnabled​(double limit)
        Description copied from interface: AngularLimitsJoint
        Sets both the lower and upper limits to the given limit and enables them.

        See the class documentation for more details on the limit ranges.

        Specified by:
        setLimitsEnabled in interface AngularLimitsJoint
        Parameters:
        limit - the desired limit

      • getLimitsReferenceAngle

        public double getLimitsReferenceAngle()
        Description copied from interface: AngularLimitsJoint
        Returns the limits reference angle.

        The reference angle is the angle calculated when the joint was created from the two joined bodies. The reference angle is the angular difference between the bodies.

        Specified by:
        getLimitsReferenceAngle in interface AngularLimitsJoint
        Returns:
        double

      • setLimitsReferenceAngle

        public void setLimitsReferenceAngle​(double angle)
        Description copied from interface: AngularLimitsJoint
        Sets the limits reference angle.

        This method can be used to set the reference angle to override the computed reference angle from the constructor. This is useful in recreating the joint from a current state or when adjusting the limits.

        See the class documentation for more details.

        Specified by:
        setLimitsReferenceAngle in interface AngularLimitsJoint
        Parameters:
        angle - the reference angle in radians
        See Also:
        AngularLimitsJoint.getLimitsReferenceAngle()