00001 /* 00002 * Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com 00003 * 00004 * This software is provided 'as-is', without any express or implied 00005 * warranty. In no event will the authors be held liable for any damages 00006 * arising from the use of this software. 00007 * Permission is granted to anyone to use this software for any purpose, 00008 * including commercial applications, and to alter it and redistribute it 00009 * freely, subject to the following restrictions: 00010 * 1. The origin of this software must not be misrepresented; you must not 00011 * claim that you wrote the original software. If you use this software 00012 * in a product, an acknowledgment in the product documentation would be 00013 * appreciated but is not required. 00014 * 2. Altered source versions must be plainly marked as such, and must not be 00015 * misrepresented as being the original software. 00016 * 3. This notice may not be removed or altered from any source distribution. 00017 */ 00018 00019 #ifndef B2_FRICTION_JOINT_H 00020 #define B2_FRICTION_JOINT_H 00021 00022 #include <Box2D/Dynamics/Joints/b2Joint.h> 00023 00025 struct b2FrictionJointDef : public b2JointDef 00026 { 00027 b2FrictionJointDef() 00028 { 00029 type = e_frictionJoint; 00030 localAnchorA.SetZero(); 00031 localAnchorB.SetZero(); 00032 maxForce = 0.0f; 00033 maxTorque = 0.0f; 00034 } 00035 00038 void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor); 00039 00041 b2Vec2 localAnchorA; 00042 00044 b2Vec2 localAnchorB; 00045 00047 float32 maxForce; 00048 00050 float32 maxTorque; 00051 }; 00052 00055 class b2FrictionJoint : public b2Joint 00056 { 00057 public: 00058 b2Vec2 GetAnchorA() const; 00059 b2Vec2 GetAnchorB() const; 00060 00061 b2Vec2 GetReactionForce(float32 inv_dt) const; 00062 float32 GetReactionTorque(float32 inv_dt) const; 00063 00065 void SetMaxForce(float32 force); 00066 00068 float32 GetMaxForce() const; 00069 00071 void SetMaxTorque(float32 torque); 00072 00074 float32 GetMaxTorque() const; 00075 00076 protected: 00077 00078 friend class b2Joint; 00079 00080 b2FrictionJoint(const b2FrictionJointDef* def); 00081 00082 void InitVelocityConstraints(const b2TimeStep& step); 00083 void SolveVelocityConstraints(const b2TimeStep& step); 00084 bool SolvePositionConstraints(float32 baumgarte); 00085 00086 b2Vec2 m_localAnchorA; 00087 b2Vec2 m_localAnchorB; 00088 00089 b2Mat22 m_linearMass; 00090 float32 m_angularMass; 00091 00092 b2Vec2 m_linearImpulse; 00093 float32 m_angularImpulse; 00094 00095 float32 m_maxForce; 00096 float32 m_maxTorque; 00097 }; 00098 00099 #endif