org.jbox2d.dynamics.joints.WheelJointDef Maven / Gradle / Ivy

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 * Copyright (c) 2013, Daniel Murphy
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/**
 * Created at 7:27:31 AM Jan 21, 2011
 */
package org.jbox2d.dynamics.joints;

import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;

/**
 * Wheel joint definition. This requires defining a line of motion using an axis and an anchor
 * point. The definition uses local anchor points and a local axis so that the initial configuration
 * can violate the constraint slightly. The joint translation is zero when the local anchor points
 * coincide in world space. Using local anchors and a local axis helps when saving and loading a
 * game.
 * 
 * @author Daniel Murphy
 */
public class WheelJointDef extends JointDef {

  /**
   * The local anchor point relative to body1's origin.
   */
  public final Vec2 localAnchorA = new Vec2();

  /**
   * The local anchor point relative to body2's origin.
   */
  public final Vec2 localAnchorB = new Vec2();

  /**
   * The local translation axis in body1.
   */
  public final Vec2 localAxisA = new Vec2();

  /**
   * Enable/disable the joint motor.
   */
  public boolean enableMotor;

  /**
   * The maximum motor torque, usually in N-m.
   */
  public float maxMotorTorque;

  /**
   * The desired motor speed in radians per second.
   */
  public float motorSpeed;

  /**
   * Suspension frequency, zero indicates no suspension
   */
  public float frequencyHz;

  /**
   * Suspension damping ratio, one indicates critical damping
   */
  public float dampingRatio;

  public WheelJointDef() {
    super(JointType.WHEEL);
    localAxisA.set(1, 0);
    enableMotor = false;
    maxMotorTorque = 0f;
    motorSpeed = 0f;
  }

  public void initialize(Body b1, Body b2, Vec2 anchor, Vec2 axis) {
    bodyA = b1;
    bodyB = b2;
    b1.getLocalPointToOut(anchor, localAnchorA);
    b2.getLocalPointToOut(anchor, localAnchorB);
    bodyA.getLocalVectorToOut(axis, localAxisA);
  }
}