DistanceJointDef.java

/*
 * JBox2D - A Java Port of Erin Catto's Box2D
 * 
 * JBox2D homepage: http://jbox2d.sourceforge.net/
 * Box2D homepage: http://www.box2d.org
 * 
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 * 
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 * 
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software
 * in a product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

package org.jbox2d.dynamics.joints;

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

//Updated to rev 56->130->142 of b2DistanceJoint.cpp/.h

/**
 * Definition for a distance joint.  A distance joint
 * keeps two points on two bodies at a constant distance
 * from each other.
 */
public class DistanceJointDef extends JointDef {
	/** The local anchor point relative to body1's origin. */
	public Vec2 localAnchor1;

	/** The local anchor point relative to body2's origin. */
	public Vec2 localAnchor2;

	/** The equilibrium length between the anchor points. */
	public float length;

	public float frequencyHz;

	public float dampingRatio;

	public DistanceJointDef() {
		type = JointType.DISTANCE_JOINT;
		localAnchor1 = new Vec2(0.0f, 0.0f);
		localAnchor2 = new Vec2(0.0f, 0.0f);
		length = 1.0f;
		frequencyHz = 0.0f;
		dampingRatio = 0.0f;
	}

	/**
	 * Initialize the bodies, anchors, and length using the world
	 * anchors.
	 * @param b1 First body
	 * @param b2 Second body
	 * @param anchor1 World anchor on first body
	 * @param anchor2 World anchor on second body
	 */
	public void initialize(final Body b1, final Body b2, final Vec2 anchor1, final Vec2 anchor2) {
		body1 = b1;
		body2 = b2;
		localAnchor1.set(body1.getLocalPoint(anchor1));
		localAnchor2.set(body2.getLocalPoint(anchor2));
		final Vec2 d = anchor2.sub(anchor1);
		length = d.length();
	}
}