b2_wheel_joint.h

// 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