DistanceJointDef.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.physics.box2d.joints;

import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.JointDef;

/**
 * Distance joint definition. This requires defining an anchor point on both bodies and the non-zero length of the
 * distance joint. The definition uses local anchor points so that the initial configuration can violate the constraint
 * slightly. This helps when saving and loading a game.
 * 
 * @warning Do not use a zero or short length.
 */
public class DistanceJointDef extends JointDef {
	public DistanceJointDef() {
		type = JointType.DistanceJoint;
	}

	/** Initialize the bodies, anchors, and length using the world anchors. */
	public void initialize(Body bodyA, Body bodyB, Vector2 anchorA, Vector2 anchorB) {
		this.bodyA = bodyA;
		this.bodyB = bodyB;
		this.localAnchorA.set(bodyA.getLocalPoint(anchorA));
		this.localAnchorB.set(bodyB.getLocalPoint(anchorB));
		this.length = anchorA.dst(anchorB);
	}

	/** The local anchor point relative to body1's origin. */
	public final Vector2 localAnchorA = new Vector2();

	/** The local anchor point relative to body2's origin. */
	public final Vector2 localAnchorB = new Vector2();

	/** The natural length between the anchor points. */
	public float length = 1;

	/** The mass-spring-damper frequency in Hertz. */
	public float frequencyHz = 0;

	/** The damping ratio. 0 = no damping, 1 = critical damping. */
	public float dampingRatio = 0;
}