/******************************************************************************* * 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. * * Neither the name of the <organization> nor the * names of its contributors may be used to endorse or promote products * derived from this software without specific prior written permission. * * 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 DANIEL MURPHY 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; } }