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A 2D java physics engine, a port of the C++ Box2d engine. This is the core physics engine.
/*******************************************************************************
* Copyright (c) 2011, Daniel Murphy
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
******************************************************************************/
/**
* Created at 12:11:41 PM Jan 23, 2011
*/
package org.jbox2d.dynamics.joints;
import org.jbox2d.common.Settings;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
/**
* Pulley joint definition. This requires two ground anchors,
* two dynamic body anchor points, max lengths for each side,
* and a pulley ratio.
*
* @author Daniel Murphy
*/
public class PulleyJointDef extends JointDef {
/**
* The first ground anchor in world coordinates. This point never moves.
*/
public Vec2 groundAnchorA;
/**
* The second ground anchor in world coordinates. This point never moves.
*/
public Vec2 groundAnchorB;
/**
* The local anchor point relative to bodyA's origin.
*/
public Vec2 localAnchorA;
/**
* The local anchor point relative to bodyB's origin.
*/
public Vec2 localAnchorB;
/**
* The a reference length for the segment attached to bodyA.
*/
public float lengthA;
/**
* The maximum length of the segment attached to bodyA.
*/
public float maxLengthA;
/**
* The a reference length for the segment attached to bodyB.
*/
public float lengthB;
/**
* The maximum length of the segment attached to bodyB.
*/
public float maxLengthB;
/**
* The pulley ratio, used to simulate a block-and-tackle.
*/
public float ratio;
public PulleyJointDef() {
type = JointType.PULLEY;
groundAnchorA = new Vec2(-1.0f, 1.0f);
groundAnchorB = new Vec2(1.0f, 1.0f);
localAnchorA = new Vec2(-1.0f, 0.0f);
localAnchorB = new Vec2(1.0f, 0.0f);
lengthA = 0.0f;
maxLengthA = 0.0f;
lengthB = 0.0f;
maxLengthB = 0.0f;
ratio = 1.0f;
collideConnected = true;
}
/**
* Initialize the bodies, anchors, lengths, max lengths, and ratio using the world
* anchors.
*/
public void initialize(Body b1, Body b2, Vec2 ga1, Vec2 ga2, Vec2 anchor1, Vec2 anchor2, float r) {
bodyA = b1;
bodyB = b2;
groundAnchorA = ga1;
groundAnchorB = ga2;
localAnchorA = bodyA.getLocalPoint(anchor1);
localAnchorB = bodyB.getLocalPoint(anchor2);
Vec2 d1 = anchor1.sub(ga1);
lengthA = d1.length();
Vec2 d2 = anchor2.sub(ga2);
lengthB = d2.length();
ratio = r;
assert (ratio > Settings.EPSILON);
float C = lengthA + ratio * lengthB;
maxLengthA = C - ratio * PulleyJoint.MIN_PULLEY_LENGTH;
maxLengthB = (C - PulleyJoint.MIN_PULLEY_LENGTH) / ratio;
}
}