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# Box2D/Box2D/Dynamics/Joints/b2FrictionJoint.h

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    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