b2PulleyJoint.h

Go to the documentation of this file.

/*
* Copyright (c) 2006-2011 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_PULLEY_JOINT_H
#define B2_PULLEY_JOINT_H

#include <Box2D/Dynamics/Joints/b2Joint.h>

const float32 b2_minPulleyLength = 2.0f;

struct b2PulleyJointDef : public b2JointDef
{
        b2PulleyJointDef()
        {
                type = e_pulleyJoint;
                groundAnchorA.Set(-1.0f, 1.0f);
                groundAnchorB.Set(1.0f, 1.0f);
                localAnchorA.Set(-1.0f, 0.0f);
                localAnchorB.Set(1.0f, 0.0f);
                lengthA = 0.0f;
                lengthB = 0.0f;
                ratio = 1.0f;
                collideConnected = true;
        }

        void Initialize(b2Body* bodyA, b2Body* bodyB,
                                        const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
                                        const b2Vec2& anchorA, const b2Vec2& anchorB,
                                        float32 ratio);

        b2Vec2 groundAnchorA;

        b2Vec2 groundAnchorB;

        b2Vec2 localAnchorA;

        b2Vec2 localAnchorB;

        float32 lengthA;

        float32 lengthB;

        float32 ratio;
};

class b2PulleyJoint : public b2Joint
{
public:
        b2Vec2 GetAnchorA() const;
        b2Vec2 GetAnchorB() const;

        b2Vec2 GetReactionForce(float32 inv_dt) const;
        float32 GetReactionTorque(float32 inv_dt) const;

        b2Vec2 GetGroundAnchorA() const;

        b2Vec2 GetGroundAnchorB() const;

        float32 GetLengthA() const;

        float32 GetLengthB() const;

        float32 GetRatio() const;

        float32 GetCurrentLengthA() const;

        float32 GetCurrentLengthB() const;

        void Dump();

        void ShiftOrigin(const b2Vec2& newOrigin);

protected:

        friend class b2Joint;
        b2PulleyJoint(const b2PulleyJointDef* data);

        void InitVelocityConstraints(const b2SolverData& data);
        void SolveVelocityConstraints(const b2SolverData& data);
        bool SolvePositionConstraints(const b2SolverData& data);

        b2Vec2 m_groundAnchorA;
        b2Vec2 m_groundAnchorB;
        float32 m_lengthA;
        float32 m_lengthB;
        
        // Solver shared
        b2Vec2 m_localAnchorA;
        b2Vec2 m_localAnchorB;
        float32 m_constant;
        float32 m_ratio;
        float32 m_impulse;

        // Solver temp
        int32 m_indexA;
        int32 m_indexB;
        b2Vec2 m_uA;
        b2Vec2 m_uB;
        b2Vec2 m_rA;
        b2Vec2 m_rB;
        b2Vec2 m_localCenterA;
        b2Vec2 m_localCenterB;
        float32 m_invMassA;
        float32 m_invMassB;
        float32 m_invIA;
        float32 m_invIB;
        float32 m_mass;
};

#endif