b2_wheel_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_WHEEL_JOINT_H
#define B2_WHEEL_JOINT_H

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

struct B2_API b2WheelJointDef : public b2JointDef
{
        b2WheelJointDef()
        {
                type = e_wheelJoint;
                localAnchorA.SetZero();
                localAnchorB.SetZero();
                localAxisA.Set(1.0f, 0.0f);
                enableLimit = false;
                lowerTranslation = 0.0f;
                upperTranslation = 0.0f;
                enableMotor = false;
                maxMotorTorque = 0.0f;
                motorSpeed = 0.0f;
                stiffness = 0.0f;
                damping = 0.0f;
        }

        void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);

        b2Vec2 localAnchorA;

        b2Vec2 localAnchorB;

        b2Vec2 localAxisA;

        bool enableLimit;

        float lowerTranslation;

        float upperTranslation;

        bool enableMotor;

        float maxMotorTorque;

        float motorSpeed;

        float stiffness;

        float damping;
};

class B2_API b2WheelJoint : 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;

        const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }

        const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }

        const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; }

        float GetJointTranslation() const;

        float GetJointLinearSpeed() const;

        float GetJointAngle() const;

        float GetJointAngularSpeed() const;

        bool IsLimitEnabled() const;

        void EnableLimit(bool flag);

        float GetLowerLimit() const;

        float GetUpperLimit() const;

        void SetLimits(float lower, float upper);

        bool IsMotorEnabled() const;

        void EnableMotor(bool flag);

        void SetMotorSpeed(float speed);

        float GetMotorSpeed() const;

        void SetMaxMotorTorque(float torque);
        float GetMaxMotorTorque() const;

        float GetMotorTorque(float inv_dt) const;

        void SetStiffness(float stiffness);
        float GetStiffness() const;

        void SetDamping(float damping);
        float GetDamping() const;

        void Dump() override;

        void Draw(b2Draw* draw) const override;

protected:

        friend class b2Joint;
        b2WheelJoint(const b2WheelJointDef* def);

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

        b2Vec2 m_localAnchorA;
        b2Vec2 m_localAnchorB;
        b2Vec2 m_localXAxisA;
        b2Vec2 m_localYAxisA;

        float m_impulse;
        float m_motorImpulse;
        float m_springImpulse;

        float m_lowerImpulse;
        float m_upperImpulse;
        float m_translation;
        float m_lowerTranslation;
        float m_upperTranslation;

        float m_maxMotorTorque;
        float m_motorSpeed;

        bool m_enableLimit;
        bool m_enableMotor;

        float m_stiffness;
        float m_damping;

        // Solver temp
        int32 m_indexA;
        int32 m_indexB;
        b2Vec2 m_localCenterA;
        b2Vec2 m_localCenterB;
        float m_invMassA;
        float m_invMassB;
        float m_invIA;
        float m_invIB;

        b2Vec2 m_ax, m_ay;
        float m_sAx, m_sBx;
        float m_sAy, m_sBy;

        float m_mass;
        float m_motorMass;
        float m_axialMass;
        float m_springMass;

        float m_bias;
        float m_gamma;

};

inline float b2WheelJoint::GetMotorSpeed() const
{
        return m_motorSpeed;
}

inline float b2WheelJoint::GetMaxMotorTorque() const
{
        return m_maxMotorTorque;
}

#endif