/* * Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com * * 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; protected: friend class b2Joint; b2MouseJoint(const b2MouseJointDef* def); void InitVelocityConstraints(const b2TimeStep& step); void SolveVelocityConstraints(const b2TimeStep& step); bool SolvePositionConstraints(float32 baumgarte) { B2_NOT_USED(baumgarte); return true; } b2Vec2 m_localAnchor; b2Vec2 m_target; b2Vec2 m_impulse; b2Mat22 m_mass; // effective mass for point-to-point constraint. b2Vec2 m_C; // position error float32 m_maxForce; float32 m_frequencyHz; float32 m_dampingRatio; float32 m_beta; float32 m_gamma; }; #endif