b2_pulley_joint.h

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// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_PULLEY_JOINT_H
#define B2_PULLEY_JOINT_H

#include "b2_api.h"
#include "b2_joint.h"

const float b2_minPulleyLength = 2.0f;

struct B2_API 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,
                                        float ratio);

        b2Vec2 groundAnchorA;

        b2Vec2 groundAnchorB;

        b2Vec2 localAnchorA;

        b2Vec2 localAnchorB;

        float lengthA;

        float lengthB;

        float ratio;
};

class B2_API b2PulleyJoint : public b2Joint
{
public:
        b2Vec2 GetAnchorA() const override;
        b2Vec2 GetAnchorB() const override;

        b2Vec2 GetReactionForce(float inv_dt) const override;
        float GetReactionTorque(float inv_dt) const override;

        b2Vec2 GetGroundAnchorA() const;

        b2Vec2 GetGroundAnchorB() const;

        float GetLengthA() const;

        float GetLengthB() const;

        float GetRatio() const;

        float GetCurrentLengthA() const;

        float GetCurrentLengthB() const;

        void Dump() override;

        void ShiftOrigin(const b2Vec2& newOrigin) override;

protected:

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

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

        b2Vec2 m_groundAnchorA;
        b2Vec2 m_groundAnchorB;
        float m_lengthA;
        float m_lengthB;

        // Solver shared
        b2Vec2 m_localAnchorA;
        b2Vec2 m_localAnchorB;
        float m_constant;
        float m_ratio;
        float 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;
        float m_invMassA;
        float m_invMassB;
        float m_invIA;
        float m_invIB;
        float m_mass;
};

#endif