b2_gear_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_GEAR_JOINT_H
#define B2_GEAR_JOINT_H

#include "b2_joint.h"

struct B2_API b2GearJointDef : public b2JointDef
{
        b2GearJointDef()
        {
                type = e_gearJoint;
                joint1 = nullptr;
                joint2 = nullptr;
                ratio = 1.0f;
        }

        b2Joint* joint1;

        b2Joint* joint2;

        float ratio;
};

class B2_API b2GearJoint : 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;

        b2Joint* GetJoint1() { return m_joint1; }

        b2Joint* GetJoint2() { return m_joint2; }

        void SetRatio(float ratio);
        float GetRatio() const;

        void Dump() override;

protected:

        friend class b2Joint;
        b2GearJoint(const b2GearJointDef* data);

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

        b2Joint* m_joint1;
        b2Joint* m_joint2;

        b2JointType m_typeA;
        b2JointType m_typeB;

        // Body A is connected to body C
        // Body B is connected to body D
        b2Body* m_bodyC;
        b2Body* m_bodyD;

        // Solver shared
        b2Vec2 m_localAnchorA;
        b2Vec2 m_localAnchorB;
        b2Vec2 m_localAnchorC;
        b2Vec2 m_localAnchorD;

        b2Vec2 m_localAxisC;
        b2Vec2 m_localAxisD;

        float m_referenceAngleA;
        float m_referenceAngleB;

        float m_constant;
        float m_ratio;

        float m_impulse;

        // Solver temp
        int32 m_indexA, m_indexB, m_indexC, m_indexD;
        b2Vec2 m_lcA, m_lcB, m_lcC, m_lcD;
        float m_mA, m_mB, m_mC, m_mD;
        float m_iA, m_iB, m_iC, m_iD;
        b2Vec2 m_JvAC, m_JvBD;
        float m_JwA, m_JwB, m_JwC, m_JwD;
        float m_mass;
};

#endif