text: /*
  * Copyright (c) 2006-2007 Erin Catto 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.
  */
  
  #ifndef B2_MOUSE_JOINT_H
  #define B2_MOUSE_JOINT_H
  
  #include <Box2D/Dynamics/Joints/b2Joint.h>
  
  /// Mouse joint definition. This requires a world target point,
  /// tuning parameters, and the time step.
  struct b2MouseJointDef : public b2JointDef
  {
  	b2MouseJointDef()
  	{
  		type = e_mouseJoint;
  		target.Set(0.0f, 0.0f);
  		maxForce = 0.0f;
  		frequencyHz = 5.0f;
  		dampingRatio = 0.7f;
  	}
  
  	/// The initial world target point. This is assumed
  	/// to coincide with the body anchor initially.
  	b2Vec2 target;
  
  	/// The maximum constraint force that can be exerted
  	/// to move the candidate body. Usually you will express
  	/// as some multiple of the weight (multiplier * mass * gravity).
  	float32 maxForce;
  
  	/// The response speed.
  	float32 frequencyHz;
  
  	/// The damping ratio. 0 = no damping, 1 = critical damping.
  	float32 dampingRatio;
  };
  
  /// A mouse joint is used to make a point on a body track a
  /// specified world point. This a soft constraint with a maximum
  /// force. This allows the constraint to stretch and without
  /// applying huge forces.
  /// NOTE: this joint is not documented in the manual because it was
  /// developed to be used in the testbed. If you want to learn how to
  /// use the mouse joint, look at the testbed.
  class b2MouseJoint : public b2Joint
  {
  public:
  
  	/// Implements b2Joint.
  	b2Vec2 GetAnchorA() const;
  
  	/// Implements b2Joint.
  	b2Vec2 GetAnchorB() const;
  
  	/// Implements b2Joint.
  	b2Vec2 GetReactionForce(float32 inv_dt) const;
  
  	/// Implements b2Joint.
  	float32 GetReactionTorque(float32 inv_dt) const;
  
  	/// Use this to update the target point.
  	void SetTarget(const b2Vec2& target);
  	const b2Vec2& GetTarget() const;
  
  	/// Set/get the maximum force in Newtons.
  	void SetMaxForce(float32 force);
  	float32 GetMaxForce() const;
  
  	/// Set/get the frequency in Hertz.
  	void SetFrequency(float32 hz);
  	float32 GetFrequency() const;
  
  	/// Set/get the damping ratio (dimensionless).
  	void SetDampingRatio(float32 ratio);
  	float32 GetDampingRatio() const;
  
  	/// The mouse joint does not support dumping.
  	void Dump() { b2Log("Mouse joint dumping is not supported.\n"); }
  
  	/// Implement b2Joint::ShiftOrigin
  	void ShiftOrigin(const b2Vec2& newOrigin);
  
  protected:
  	friend class b2Joint;
  
  	b2MouseJoint(const b2MouseJointDef* def);
  
  	void InitVelocityConstraints(const b2SolverData& data);
  	void SolveVelocityConstraints(const b2SolverData& data);
  	bool SolvePositionConstraints(const b2SolverData& data);
  
  	b2Vec2 m_localAnchorB;
  	b2Vec2 m_targetA;
  	float32 m_frequencyHz;
  	float32 m_dampingRatio;
  	float32 m_beta;
  	
  	// Solver shared
  	b2Vec2 m_impulse;
  	float32 m_maxForce;
  	float32 m_gamma;
  
  	// Solver temp
  	int32 m_indexA;
  	int32 m_indexB;
  	b2Vec2 m_rB;
  	b2Vec2 m_localCenterB;
  	float32 m_invMassB;
  	float32 m_invIB;
  	b2Mat22 m_mass;
  	b2Vec2 m_C;
  };
  
  #endif
  