/*
  * Copyright (c) 2006-2007 Erin Catto 
* 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, and must not be
* misrepresented the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/

// Point-to-point constraint
// C = p2 - p1
// Cdot = v2 - v1
//      = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)

// Motor constraint
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2

var b2RevoluteJoint = Class.create();
Object.extend(b2RevoluteJoint.prototype, b2Joint.prototype);
Object.extend(b2RevoluteJoint.prototype, 
{
        GetAnchor1: function(){
                var tMat = this.m_body1.m_R;
                return new b2Vec2(        this.m_body1.m_position.x + (tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y),
                                                        this.m_body1.m_position.y + (tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y));
        },
        GetAnchor2: function(){
                var tMat = this.m_body2.m_R;
                return new b2Vec2(        this.m_body2.m_position.x + (tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y),
                                                        this.m_body2.m_position.y + (tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y));
        },
        GetJointAngle: function(){
                return this.m_body2.m_rotation - this.m_body1.m_rotation;
        },
        GetJointSpeed: function(){
                return this.m_body2.m_angularVelocity - this.m_body1.m_angularVelocity;
        },
        GetMotorTorque: function(invTimeStep){
                return  invTimeStep * this.m_motorImpulse;
        },

        SetMotorSpeed: function(speed)
        {
                this.m_motorSpeed = speed;
        },

        SetMotorTorque: function(torque)
        {
                this.m_maxMotorTorque = torque;
        },

        GetReactionForce: function(invTimeStep)
        {
                var tVec = this.m_ptpImpulse.Copy();
                tVec.Multiply(invTimeStep);
                //return invTimeStep * this.m_ptpImpulse;
                return tVec;
        },

        GetReactionTorque: function(invTimeStep)
        {
                return invTimeStep * this.m_limitImpulse;
        },

        //--------------- Internals Below -------------------

        initialize: function(def){
                // The constructor for b2Joint
                // initialize instance variables for references
                this.m_node1 = new b2JointNode();
                this.m_node2 = new b2JointNode();
                //
                this.m_type = def.type;
                this.m_prev = null;
                this.m_next = null;
                this.m_body1 = def.body1;
                this.m_body2 = def.body2;
                this.m_collideConnected = def.collideConnected;
                this.m_islandFlag = false;
                this.m_userData = def.userData;
                //

                // initialize instance variables for references
                this.K = new b2Mat22();
                this.K1 = new b2Mat22();
                this.K2 = new b2Mat22();
                this.K3 = new b2Mat22();
                this.m_localAnchor1 = new b2Vec2();
                this.m_localAnchor2 = new b2Vec2();
                this.m_ptpImpulse = new b2Vec2();
                this.m_ptpMass = new b2Mat22();
                //

                //super(def);

                var tMat;
                var tX;
                var tY;

                //this.m_localAnchor1 = b2Math.b2MulTMV(this.m_body1.m_R, b2Math.SubtractVV( def.anchorPoint, this.m_body1.m_position));
                tMat = this.m_body1.m_R;
                tX = def.anchorPoint.x - this.m_body1.m_position.x;
                tY = def.anchorPoint.y - this.m_body1.m_position.y;
                this.m_localAnchor1.x = tX * tMat.col1.x + tY * tMat.col1.y;
                this.m_localAnchor1.y = tX * tMat.col2.x + tY * tMat.col2.y;
                //this.m_localAnchor2 = b2Math.b2MulTMV(this.m_body2.m_R, b2Math.SubtractVV( def.anchorPoint, this.m_body2.m_position));
                tMat = this.m_body2.m_R;
                tX = def.anchorPoint.x - this.m_body2.m_position.x;
                tY = def.anchorPoint.y - this.m_body2.m_position.y;
                this.m_localAnchor2.x = tX * tMat.col1.x + tY * tMat.col1.y;
                this.m_localAnchor2.y = tX * tMat.col2.x + tY * tMat.col2.y;

                this.m_intialAngle = this.m_body2.m_rotation - this.m_body1.m_rotation;

                this.m_ptpImpulse.Set(0.0, 0.0);
                this.m_motorImpulse = 0.0;
                this.m_limitImpulse = 0.0;
                this.m_limitPositionImpulse = 0.0;

                this.m_lowerAngle = def.lowerAngle;
                this.m_upperAngle = def.upperAngle;
                this.m_maxMotorTorque = def.motorTorque;
                this.m_motorSpeed = def.motorSpeed;
                this.m_enableLimit = def.enableLimit;
                this.m_enableMotor = def.enableMotor;
        },

        // internal vars
        K: new b2Mat22(),
        K1: new b2Mat22(),
        K2: new b2Mat22(),
        K3: new b2Mat22(),
        PrepareVelocitySolver: function(){
                var b1 = this.m_body1;
                var b2 = this.m_body2;

                var tMat;

                // Compute the effective mass matrix.
                //b2Vec2 r1 = b2Mul(b1->m_R, this.m_localAnchor1);
                tMat = b1.m_R;
                var r1X = tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y;
                var r1Y = tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y;
                //b2Vec2 r2 = b2Mul(b2->m_R, this.m_localAnchor2);
                tMat = b2.m_R;
                var r2X = tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y;
                var r2Y = tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y;

                // this.K    = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)]
                //      = [1/m1+1/m2     0    ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y]
                //        [    0     1/m1+1/m2]           [-r1.x*r1.y r1.x*r1.x]           [-r1.x*r1.y r1.x*r1.x]
                var invMass1 = b1.m_invMass;
                var invMass2 = b2.m_invMass;
                var invI1 = b1.m_invI;
                var invI2 = b2.m_invI;

                //var this.K1 = new b2Mat22();
                this.K1.col1.x = invMass1 + invMass2;        this.K1.col2.x = 0.0;
                this.K1.col1.y = 0.0;                                        this.K1.col2.y = invMass1 + invMass2;

                //var this.K2 = new b2Mat22();
                this.K2.col1.x =  invI1 * r1Y * r1Y;        this.K2.col2.x = -invI1 * r1X * r1Y;
                this.K2.col1.y = -invI1 * r1X * r1Y;        this.K2.col2.y =  invI1 * r1X * r1X;

                //var this.K3 = new b2Mat2
  *
  * 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, and must not be
  * misrepresented the original software.
  * 3. This notice may not be removed or altered from any source distribution.
  */
  
  // Point-to-point constraint
  // C = p2 - p1
  // Cdot = v2 - v1
  //      = v2 + cross(w2, r2) - v1 - cross(w1, r1)
  // J = [-I -r1_skew I r2_skew ]
  // Identity used:
  // w k % (rx i + ry j) = w * (-ry i + rx j)
  
  // Motor constraint
  // Cdot = w2 - w1
  // J = [0 0 -1 0 0 1]
  // K = invI1 + invI2
  
  var b2RevoluteJoint = Class.create();
  Object.extend(b2RevoluteJoint.prototype, b2Joint.prototype);
  Object.extend(b2RevoluteJoint.prototype, 
  {
          GetAnchor1: function(){
                  var tMat = this.m_body1.m_R;
                  return new b2Vec2(        this.m_body1.m_position.x + (tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y),
                                                          this.m_body1.m_position.y + (tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y));
          },
          GetAnchor2: function(){
                  var tMat = this.m_body2.m_R;
                  return new b2Vec2(        this.m_body2.m_position.x + (tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y),
                                                          this.m_body2.m_position.y + (tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y));
          },
          GetJointAngle: function(){
                  return this.m_body2.m_rotation - this.m_body1.m_rotation;
          },
          GetJointSpeed: function(){
                  return this.m_body2.m_angularVelocity - this.m_body1.m_angularVelocity;
          },
          GetMotorTorque: function(invTimeStep){
                  return  invTimeStep * this.m_motorImpulse;
          },
  
          SetMotorSpeed: function(speed)
          {
                  this.m_motorSpeed = speed;
          },
  
          SetMotorTorque: function(torque)
          {
                  this.m_maxMotorTorque = torque;
          },
  
          GetReactionForce: function(invTimeStep)
          {
                  var tVec = this.m_ptpImpulse.Copy();
                  tVec.Multiply(invTimeStep);
                  //return invTimeStep * this.m_ptpImpulse;
                  return tVec;
          },
  
          GetReactionTorque: function(invTimeStep)
          {
                  return invTimeStep * this.m_limitImpulse;
          },
  
          //--------------- Internals Below -------------------
  
          initialize: function(def){
                  // The constructor for b2Joint
                  // initialize instance variables for references
                  this.m_node1 = new b2JointNode();
                  this.m_node2 = new b2JointNode();
                  //
                  this.m_type = def.type;
                  this.m_prev = null;
                  this.m_next = null;
                  this.m_body1 = def.body1;
                  this.m_body2 = def.body2;
                  this.m_collideConnected = def.collideConnected;
                  this.m_islandFlag = false;
                  this.m_userData = def.userData;
                  //
  
                  // initialize instance variables for references
                  this.K = new b2Mat22();
                  this.K1 = new b2Mat22();
                  this.K2 = new b2Mat22();
                  this.K3 = new b2Mat22();
                  this.m_localAnchor1 = new b2Vec2();
                  this.m_localAnchor2 = new b2Vec2();
                  this.m_ptpImpulse = new b2Vec2();
                  this.m_ptpMass = new b2Mat22();
                  //
  
                  //super(def);
  
                  var tMat;
                  var tX;
                  var tY;
  
                  //this.m_localAnchor1 = b2Math.b2MulTMV(this.m_body1.m_R, b2Math.SubtractVV( def.anchorPoint, this.m_body1.m_position));
                  tMat = this.m_body1.m_R;
                  tX = def.anchorPoint.x - this.m_body1.m_position.x;
                  tY = def.anchorPoint.y - this.m_body1.m_position.y;
                  this.m_localAnchor1.x = tX * tMat.col1.x + tY * tMat.col1.y;
                  this.m_localAnchor1.y = tX * tMat.col2.x + tY * tMat.col2.y;
                  //this.m_localAnchor2 = b2Math.b2MulTMV(this.m_body2.m_R, b2Math.SubtractVV( def.anchorPoint, this.m_body2.m_position));
                  tMat = this.m_body2.m_R;
                  tX = def.anchorPoint.x - this.m_body2.m_position.x;
                  tY = def.anchorPoint.y - this.m_body2.m_position.y;
                  this.m_localAnchor2.x = tX * tMat.col1.x + tY * tMat.col1.y;
                  this.m_localAnchor2.y = tX * tMat.col2.x + tY * tMat.col2.y;
  
                  this.m_intialAngle = this.m_body2.m_rotation - this.m_body1.m_rotation;
  
                  this.m_ptpImpulse.Set(0.0, 0.0);
                  this.m_motorImpulse = 0.0;
                  this.m_limitImpulse = 0.0;
                  this.m_limitPositionImpulse = 0.0;
  
                  this.m_lowerAngle = def.lowerAngle;
                  this.m_upperAngle = def.upperAngle;
                  this.m_maxMotorTorque = def.motorTorque;
                  this.m_motorSpeed = def.motorSpeed;
                  this.m_enableLimit = def.enableLimit;
                  this.m_enableMotor = def.enableMotor;
          },
  
          // internal vars
          K: new b2Mat22(),
          K1: new b2Mat22(),
          K2: new b2Mat22(),
          K3: new b2Mat22(),
          PrepareVelocitySolver: function(){
                  var b1 = this.m_body1;
                  var b2 = this.m_body2;
  
                  var tMat;
  
                  // Compute the effective mass matrix.
                  //b2Vec2 r1 = b2Mul(b1->m_R, this.m_localAnchor1);
                  tMat = b1.m_R;
                  var r1X = tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y;
                  var r1Y = tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y;
                  //b2Vec2 r2 = b2Mul(b2->m_R, this.m_localAnchor2);
                  tMat = b2.m_R;
                  var r2X = tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y;
                  var r2Y = tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y;
  
                  // this.K    = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)]
                  //      = [1/m1+1/m2     0    ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y]
                  //        [    0     1/m1+1/m2]           [-r1.x*r1.y r1.x*r1.x]           [-r1.x*r1.y r1.x*r1.x]
                  var invMass1 = b1.m_invMass;
                  var invMass2 = b2.m_invMass;
                  var invI1 = b1.m_invI;
                  var invI2 = b2.m_invI;
  
                  //var this.K1 = new b2Mat22();
                  this.K1.col1.x = invMass1 + invMass2;        this.K1.col2.x = 0.0;
                  this.K1.col1.y = 0.0;                                        this.K1.col2.y = invMass1 + invMass2;
  
                  //var this.K2 = new b2Mat22();
                  this.K2.col1.x =  invI1 * r1Y * r1Y;        this.K2.col2.x = -invI1 * r1X * r1Y;
                  this.K2.col1.y = -invI1 * r1X * r1Y;        this.K2.col2.y =  invI1 * r1X * r1X;
  
                  //var this.K3 = new b2Mat22();
                  this.K3.col1.x =  invI2 * r2Y * r2Y;        this.K3.col2.x = -invI2 * r2X * r2Y;
                  this.K3.col1.y = -invI2 * r2X * r2Y;        this.K3.col2.y =  invI2 * r2X * r2X;
  
                  //var this.K = b2Math.AddMM(b2Math.AddMM(this.K1, this.K2), this.K3);
                  this.K.SetM(this.K1);
                  this.K.AddM(this.K2);
                  this.K.AddM(this.K3);
  
                  //this.m_ptpMass = this.K.Invert();
                  this.K.Invert(this.m_ptpMass);
  
                  this.m_motorMass = 1.0 / (invI1 + invI2);
  
                  if (this.m_enableMotor == false)
                  {
                          this.m_motorImpulse = 0.0;
                  }
  
                  if (this.m_enableLimit)
                  {
                          var jointAngle = b2.m_rotation - b1.m_rotation - this.m_intialAngle;
                          if (b2Math.b2Abs(this.m_upperAngle - this.m_lowerAngle) < 2.0 * b2Settings.b2_angularSlop)
                          {
                                  this.m_limitState = b2Joint.e_equalLimits;
                          }
                          else if (jointAngle <= this.m_lowerAngle)
                          {
                                  if (this.m_limitState != b2Joint.e_atLowerLimit)
                                  {
                                          this.m_limitImpulse = 0.0;
                                  }
                                  this.m_limitState = b2Joint.e_atLowerLimit;
                          }
                          else if (jointAngle >= this.m_upperAngle)
                          {
                                  if (this.m_limitState != b2Joint.e_atUpperLimit)
                                  {
                                          this.m_limitImpulse = 0.0;
                                  }
                                  this.m_limitState = b2Joint.e_atUpperLimit;
                          }
                          else
                          {
                                  this.m_limitState = b2Joint.e_inactiveLimit;
                                  this.m_limitImpulse = 0.0;
                          }
                  }
                  else
                  {
                          this.m_limitImpulse = 0.0;
                  }
  
                  // Warm starting.
                  if (b2World.s_enableWarmStarting)
                  {
                          //b1.m_linearVelocity.Subtract( b2Math.MulFV( invMass1, this.m_ptpImpulse) );
                          b1.m_linearVelocity.x -= invMass1 * this.m_ptpImpulse.x;
                          b1.m_linearVelocity.y -= invMass1 * this.m_ptpImpulse.y;
                          //b1.m_angularVelocity -= invI1 * (b2Math.b2CrossVV(r1, this.m_ptpImpulse) + this.m_motorImpulse + this.m_limitImpulse);
                          b1.m_angularVelocity -= invI1 * ((r1X * this.m_ptpImpulse.y - r1Y * this.m_ptpImpulse.x) + this.m_motorImpulse + this.m_limitImpulse);
  
                          //b2.m_linearVelocity.Add( b2Math.MulFV( invMass2 , this.m_ptpImpulse ));
                          b2.m_linearVelocity.x += invMass2 * this.m_ptpImpulse.x;
                          b2.m_linearVelocity.y += invMass2 * this.m_ptpImpulse.y;
                          //b2.m_angularVelocity += invI2 * (b2Math.b2CrossVV(r2, this.m_ptpImpulse) + this.m_motorImpulse + this.m_limitImpulse);
                          b2.m_angularVelocity += invI2 * ((r2X * this.m_ptpImpulse.y - r2Y * this.m_ptpImpulse.x) + this.m_motorImpulse + this.m_limitImpulse);
                  }
                  else{
                          this.m_ptpImpulse.SetZero();
                          this.m_motorImpulse = 0.0;
                          this.m_limitImpulse = 0.0;
                  }
  
                  this.m_limitPositionImpulse = 0.0;
          },
  
          SolveVelocityConstraints: function(step){
                  var b1 = this.m_body1;
                  var b2 = this.m_body2;
  
                  var tMat;
  
                  //var r1 = b2Math.b2MulMV(b1.m_R, this.m_localAnchor1);
                  tMat = b1.m_R;
                  var r1X = tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y;
                  var r1Y = tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y;
                  //var r2 = b2Math.b2MulMV(b2.m_R, this.m_localAnchor2);
                  tMat = b2.m_R;
                  var r2X = tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y;
                  var r2Y = tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y;
  
                  var oldLimitImpulse;
  
                  // Solve point-to-point constraint
                  //b2Vec2 ptpCdot = b2.m_linearVelocity + b2Cross(b2.m_angularVelocity, r2) - b1.m_linearVelocity - b2Cross(b1.m_angularVelocity, r1);
                  var ptpCdotX = b2.m_linearVelocity.x + (-b2.m_angularVelocity * r2Y) - b1.m_linearVelocity.x - (-b1.m_angularVelocity * r1Y);
                  var ptpCdotY = b2.m_linearVelocity.y + (b2.m_angularVelocity * r2X) - b1.m_linearVelocity.y - (b1.m_angularVelocity * r1X);
  
                  //b2Vec2 ptpImpulse = -b2Mul(this.m_ptpMass, ptpCdot);
                  var ptpImpulseX = -(this.m_ptpMass.col1.x * ptpCdotX + this.m_ptpMass.col2.x * ptpCdotY);
                  var ptpImpulseY = -(this.m_ptpMass.col1.y * ptpCdotX + this.m_ptpMass.col2.y * ptpCdotY);
                  this.m_ptpImpulse.x += ptpImpulseX;
                  this.m_ptpImpulse.y += ptpImpulseY;
  
                  //b1->m_linearVelocity -= b1->m_invMass * ptpImpulse;
                  b1.m_linearVelocity.x -= b1.m_invMass * ptpImpulseX;
                  b1.m_linearVelocity.y -= b1.m_invMass * ptpImpulseY;
                  //b1->m_angularVelocity -= b1->m_invI * b2Cross(r1, ptpImpulse);
                  b1.m_angularVelocity -= b1.m_invI * (r1X * ptpImpulseY - r1Y * ptpImpulseX);
  
                  //b2->m_linearVelocity += b2->m_invMass * ptpImpulse;
                  b2.m_linearVelocity.x += b2.m_invMass * ptpImpulseX;
                  b2.m_linearVelocity.y += b2.m_invMass * ptpImpulseY;
                  //b2->m_angularVelocity += b2->m_invI * b2Cross(r2, ptpImpulse);
                  b2.m_angularVelocity += b2.m_invI * (r2X * ptpImpulseY - r2Y * ptpImpulseX);
  
                  if (this.m_enableMotor && this.m_limitState != b2Joint.e_equalLimits)
                  {
                          var motorCdot = b2.m_angularVelocity - b1.m_angularVelocity - this.m_motorSpeed;
                          var motorImpulse = -this.m_motorMass * motorCdot;
                          var oldMotorImpulse = this.m_motorImpulse;
                          this.m_motorImpulse = b2Math.b2Clamp(this.m_motorImpulse + motorImpulse, -step.dt * this.m_maxMotorTorque, step.dt * this.m_maxMotorTorque);
                          motorImpulse = this.m_motorImpulse - oldMotorImpulse;
                          b1.m_angularVelocity -= b1.m_invI * motorImpulse;
                          b2.m_angularVelocity += b2.m_invI * motorImpulse;
                  }
  
                  if (this.m_enableLimit && this.m_limitState != b2Joint.e_inactiveLimit)
                  {
                          var limitCdot = b2.m_angularVelocity - b1.m_angularVelocity;
                          var limitImpulse = -this.m_motorMass * limitCdot;
  
                          if (this.m_limitState == b2Joint.e_equalLimits)
                          {
                                  this.m_limitImpulse += limitImpulse;
                          }
                          else if (this.m_limitState == b2Joint.e_atLowerLimit)
                          {
                                  oldLimitImpulse = this.m_limitImpulse;
                                  this.m_limitImpulse = b2Math.b2Max(this.m_limitImpulse + limitImpulse, 0.0);
                                  limitImpulse = this.m_limitImpulse - oldLimitImpulse;
                          }
                          else if (this.m_limitState == b2Joint.e_atUpperLimit)
                          {
                                  oldLimitImpulse = this.m_limitImpulse;
                                  this.m_limitImpulse = b2Math.b2Min(this.m_limitImpulse + limitImpulse, 0.0);
                                  limitImpulse = this.m_limitImpulse - oldLimitImpulse;
                          }
  
                          b1.m_angularVelocity -= b1.m_invI * limitImpulse;
                          b2.m_angularVelocity += b2.m_invI * limitImpulse;
                  }
          },
  
          SolvePositionConstraints: function(){
  
                  var oldLimitImpulse;
                  var limitC;
  
                  var b1 = this.m_body1;
                  var b2 = this.m_body2;
  
                  var positionError = 0.0;
  
                  var tMat;
  
                  // Solve point-to-point position error.
                  //var r1 = b2Math.b2MulMV(b1.m_R, this.m_localAnchor1);
                  tMat = b1.m_R;
                  var r1X = tMat.col1.x * this.m_localAnchor1.x + tMat.col2.x * this.m_localAnchor1.y;
                  var r1Y = tMat.col1.y * this.m_localAnchor1.x + tMat.col2.y * this.m_localAnchor1.y;
                  //var r2 = b2Math.b2MulMV(b2.m_R, this.m_localAnchor2);
                  tMat = b2.m_R;
                  var r2X = tMat.col1.x * this.m_localAnchor2.x + tMat.col2.x * this.m_localAnchor2.y;
                  var r2Y = tMat.col1.y * this.m_localAnchor2.x + tMat.col2.y * this.m_localAnchor2.y;
  
                  //b2Vec2 p1 = b1->m_position + r1;
                  var p1X = b1.m_position.x + r1X;
                  var p1Y = b1.m_position.y + r1Y;
                  //b2Vec2 p2 = b2->m_position + r2;
                  var p2X = b2.m_position.x + r2X;
                  var p2Y = b2.m_position.y + r2Y;
  
                  //b2Vec2 ptpC = p2 - p1;
                  var ptpCX = p2X - p1X;
                  var ptpCY = p2Y - p1Y;
  
                  //float32 positionError = ptpC.Length();
                  positionError = Math.sqrt(ptpCX*ptpCX + ptpCY*ptpCY);
  
                  // Prevent overly large corrections.
                  //b2Vec2 dpMax(b2_maxLinearCorrection, b2_maxLinearCorrection);
                  //ptpC = b2Clamp(ptpC, -dpMax, dpMax);
  
                  //float32 invMass1 = b1->m_invMass, invMass2 = b2->m_invMass;
                  var invMass1 = b1.m_invMass;
                  var invMass2 = b2.m_invMass;
                  //float32 invI1 = b1->m_invI, invI2 = b2->m_invI;
                  var invI1 = b1.m_invI;
                  var invI2 = b2.m_invI;
  
                  //b2Mat22 this.K1;
                  this.K1.col1.x = invMass1 + invMass2;        this.K1.col2.x = 0.0;
                  this.K1.col1.y = 0.0;                                        this.K1.col2.y = invMass1 + invMass2;
  
                  //b2Mat22 this.K2;
                  this.K2.col1.x =  invI1 * r1Y * r1Y;        this.K2.col2.x = -invI1 * r1X * r1Y;
                  this.K2.col1.y = -invI1 * r1X * r1Y;        this.K2.col2.y =  invI1 * r1X * r1X;
  
                  //b2Mat22 this.K3;
                  this.K3.col1.x =  invI2 * r2Y * r2Y;                this.K3.col2.x = -invI2 * r2X * r2Y;
                  this.K3.col1.y = -invI2 * r2X * r2Y;                this.K3.col2.y =  invI2 * r2X * r2X;
  
                  //b2Mat22 this.K = this.K1 + this.K2 + this.K3;
                  this.K.SetM(this.K1);
                  this.K.AddM(this.K2);
                  this.K.AddM(this.K3);
                  //b2Vec2 impulse = this.K.Solve(-ptpC);
                  this.K.Solve(b2RevoluteJoint.tImpulse, -ptpCX, -ptpCY);
                  var impulseX = b2RevoluteJoint.tImpulse.x;
                  var impulseY = b2RevoluteJoint.tImpulse.y;
  
                  //b1.m_position -= b1.m_invMass * impulse;
                  b1.m_position.x -= b1.m_invMass * impulseX;
                  b1.m_position.y -= b1.m_invMass * impulseY;
                  //b1.m_rotation -= b1.m_invI * b2Cross(r1, impulse);
                  b1.m_rotation -= b1.m_invI * (r1X * impulseY - r1Y * impulseX);
                  b1.m_R.Set(b1.m_rotation);
  
                  //b2.m_position += b2.m_invMass * impulse;
                  b2.m_position.x += b2.m_invMass * impulseX;
                  b2.m_position.y += b2.m_invMass * impulseY;
                  //b2.m_rotation += b2.m_invI * b2Cross(r2, impulse);
                  b2.m_rotation += b2.m_invI * (r2X * impulseY - r2Y * impulseX);
                  b2.m_R.Set(b2.m_rotation);
  
                  // Handle limits.
                  var angularError = 0.0;
  
                  if (this.m_enableLimit && this.m_limitState != b2Joint.e_inactiveLimit)
                  {
                          var angle = b2.m_rotation - b1.m_rotation - this.m_intialAngle;
                          var limitImpulse = 0.0;
  
                          if (this.m_limitState == b2Joint.e_equalLimits)
                          {
                                  // Prevent large angular corrections
                                  limitC = b2Math.b2Clamp(angle, -b2Settings.b2_maxAngularCorrection, b2Settings.b2_maxAngularCorrection);
                                  limitImpulse = -this.m_motorMass * limitC;
                                  angularError = b2Math.b2Abs(limitC);
                          }
                          else if (this.m_limitState == b2Joint.e_atLowerLimit)
                          {
                                  limitC = angle - this.m_lowerAngle;
                                  angularError = b2Math.b2Max(0.0, -limitC);
  
                                  // Prevent large angular corrections and allow some slop.
                                  limitC = b2Math.b2Clamp(limitC + b2Settings.b2_angularSlop, -b2Settings.b2_maxAngularCorrection, 0.0);
                                  limitImpulse = -this.m_motorMass * limitC;
                                  oldLimitImpulse = this.m_limitPositionImpulse;
                                  this.m_limitPositionImpulse = b2Math.b2Max(this.m_limitPositionImpulse + limitImpulse, 0.0);
                                  limitImpulse = this.m_limitPositionImpulse - oldLimitImpulse;
                          }
                          else if (this.m_limitState == b2Joint.e_atUpperLimit)
                          {
                                  limitC = angle - this.m_upperAngle;
                                  angularError = b2Math.b2Max(0.0, limitC);
  
                                  // Prevent large angular corrections and allow some slop.
                                  limitC = b2Math.b2Clamp(limitC - b2Settings.b2_angularSlop, 0.0, b2Settings.b2_maxAngularCorrection);
                                  limitImpulse = -this.m_motorMass * limitC;
                                  oldLimitImpulse = this.m_limitPositionImpulse;
                                  this.m_limitPositionImpulse = b2Math.b2Min(this.m_limitPositionImpulse + limitImpulse, 0.0);
                                  limitImpulse = this.m_limitPositionImpulse - oldLimitImpulse;
                          }
  
                          b1.m_rotation -= b1.m_invI * limitImpulse;
                          b1.m_R.Set(b1.m_rotation);
                          b2.m_rotation += b2.m_invI * limitImpulse;
                          b2.m_R.Set(b2.m_rotation);
                  }
  
                  return positionError <= b2Settings.b2_linearSlop && angularError <= b2Settings.b2_angularSlop;
          },
  
          m_localAnchor1: new b2Vec2(),
          m_localAnchor2: new b2Vec2(),
          m_ptpImpulse: new b2Vec2(),
          m_motorImpulse: null,
          m_limitImpulse: null,
          m_limitPositionImpulse: null,
  
          m_ptpMass: new b2Mat22(),
          m_motorMass: null,
          m_intialAngle: null,
          m_lowerAngle: null,
          m_upperAngle: null,
          m_maxMotorTorque: null,
          m_motorSpeed: null,
  
          m_enableLimit: null,
          m_enableMotor: null,
          m_limitState: 0});
  
  b2RevoluteJoint.tImpulse = new b2Vec2();