This file comes from Box2D-JS, Copyright (c) 2008 ANDO Yasushi.
  The original version is available at http://box2d-js.sourceforge.net/ under the
  zlib/libpng license (see License.txt).
  This version has been modified to make it work with O3D.
  
  demos.crank = {};
  demos.crank.initWorld = function(world) {
    var ground = world.m_groundBody;
  
    // Define crank.
    var sd = new b2BoxDef();
    sd.extents.Set(5, 25);
    sd.density = 1.0;
  
    var bd = new b2BodyDef();
    bd.userData = g.mgr.createBox(5, 25);
    bd.AddShape(sd);
  
    var rjd = new b2RevoluteJointDef();
  
    var prevBody = ground;
  
    bd.position.Set(500/2, 210);
    bd.userData = g.mgr.createBox(5, 25);
    var body = world.CreateBody(bd);
  
    rjd.anchorPoint.Set(500/2, 235);
    rjd.body1 = prevBody;
    rjd.body2 = body;
    rjd.motorSpeed = -1.0 * Math.PI;
    rjd.motorTorque = 500000000.0;
    rjd.enableMotor = true;
    world.CreateJoint(rjd);
  
    prevBody = body;
  
    // Define follower.
    sd.extents.Set(5, 45);
    bd.position.Set(500/2, 140);
    bd.userData = g.mgr.createBox(5, 45);
    body = world.CreateBody(bd);
  
    rjd.anchorPoint.Set(500/2, 185);
    rjd.body1 = prevBody;
    rjd.body2 = body;
    rjd.enableMotor = false;
    world.CreateJoint(rjd);
  
    prevBody = body;
  
    // Define piston
    sd.extents.Set(20, 20);
    bd.position.Set(500/2, 95);
    bd.userData = g.mgr.createBox(20, 20);
    body = world.CreateBody(bd);
  
    rjd.anchorPoint.Set(500/2, 95);
    rjd.body1 = prevBody;
    rjd.body2 = body;
    world.CreateJoint(rjd);
  
    var pjd = new b2PrismaticJointDef();
    pjd.anchorPoint.Set(500/2, 95);
    pjd.body1 = ground;
    pjd.body2 = body;
    pjd.axis.Set(0.0, 1.0);
    pjd.motorSpeed = 0.0; // joint friction
    pjd.motorForce = 100000.0;
    pjd.enableMotor = true;
  
    world.CreateJoint(pjd);
  
    // Create a payload
    sd.density = 2.0;
    bd.position.Set(500/2, 10);
    bd.userData = g.mgr.createBox(20, 20);
    world.CreateBody(bd);
  }
  demos.InitWorlds.push(demos.crank.initWorld);