/*******************************************************************************
 * Copyright 2010 Mario Zechner (contact@badlogicgames.com)
 * 
 * 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;
}
