WheelJoint.hpp

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/*
 * Original work Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
 * Modified work Copyright (c) 2017 Louis Langholtz https://github.com/louis-langholtz/PlayRho
 *
 * 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 PLAYRHO_DYNAMICS_JOINTS_WHEELJOINT_HPP
#define PLAYRHO_DYNAMICS_JOINTS_WHEELJOINT_HPP
 
#include <PlayRho/Dynamics/Joints/Joint.hpp>
#include <PlayRho/Dynamics/Joints/WheelJointConf.hpp>
 
namespace playrho {
namespace d2 {
 
class WheelJoint : public Joint
{
public:
    
    WheelJoint(const WheelJointConf& def);
    
    void Accept(JointVisitor& visitor) const override;
    void Accept(JointVisitor& visitor) override;
 
    Length2 GetAnchorA() const override;
    Length2 GetAnchorB() const override;
 
    Momentum2 GetLinearReaction() const override;
    AngularMomentum GetAngularReaction() const override;
 
    Length2 GetLocalAnchorA() const { return m_localAnchorA; }
 
    Length2 GetLocalAnchorB() const  { return m_localAnchorB; }
 
    UnitVec GetLocalAxisA() const { return m_localXAxisA; }
 
    bool IsMotorEnabled() const noexcept { return m_enableMotor; }
 
    void EnableMotor(bool flag);
    
    RotInertia GetMotorMass() const noexcept { return m_motorMass; }
 
    void SetMotorSpeed(AngularVelocity speed);
 
    AngularVelocity GetMotorSpeed() const;
 
    void SetMaxMotorTorque(Torque torque);
 
    Torque GetMaxMotorTorque() const;
 
    void SetSpringFrequency(Frequency frequency);
 
    Frequency GetSpringFrequency() const;
 
    void SetSpringDampingRatio(Real ratio);
 
    Real GetSpringDampingRatio() const;
 
private:
 
    void InitVelocityConstraints(BodyConstraintsMap& bodies, const StepConf& step,
                                 const ConstraintSolverConf& conf) override;
    bool SolveVelocityConstraints(BodyConstraintsMap& bodies, const StepConf& step) override;
    bool SolvePositionConstraints(BodyConstraintsMap& bodies,
                                  const ConstraintSolverConf& conf) const override;
 
    // Solver shared
    Length2 m_localAnchorA; 
    Length2 m_localAnchorB; 
    UnitVec m_localXAxisA; 
    UnitVec m_localYAxisA; 
 
    Frequency m_frequency; 
    Real m_dampingRatio; 
 
    Momentum m_impulse = 0; 
    AngularMomentum m_motorImpulse = 0; 
    Momentum m_springImpulse = 0; 
 
    Torque m_maxMotorTorque; 
    AngularVelocity m_motorSpeed; 
    bool m_enableMotor; 
 
    // Solver temp    
    UnitVec m_ax; 
    UnitVec m_ay; 
 
    Length m_sAx; 
    Length m_sBx; 
    Length m_sAy; 
    Length m_sBy; 
 
    Mass m_mass = 0_kg; 
    RotInertia m_motorMass = RotInertia{0}; 
    Mass m_springMass = 0_kg; 
 
    LinearVelocity m_bias = 0_mps; 
    InvMass m_gamma = InvMass{0}; 
};
 
inline AngularMomentum WheelJoint::GetAngularReaction() const
{
    return m_motorImpulse;
}
 
inline AngularVelocity WheelJoint::GetMotorSpeed() const
{
    return m_motorSpeed;
}
 
inline Torque WheelJoint::GetMaxMotorTorque() const
{
    return m_maxMotorTorque;
}
 
inline void WheelJoint::SetSpringFrequency(Frequency hz)
{
    m_frequency = hz;
}
 
inline Frequency WheelJoint::GetSpringFrequency() const
{
    return m_frequency;
}
 
inline void WheelJoint::SetSpringDampingRatio(Real ratio)
{
    m_dampingRatio = ratio;
}
 
inline Real WheelJoint::GetSpringDampingRatio() const
{
    return m_dampingRatio;
}
 
// Free functions on WheelJoint instances.
 
Length GetJointTranslation(const WheelJoint& joint) noexcept;
 
AngularVelocity GetAngularVelocity(const WheelJoint& joint) noexcept;
 
inline Torque GetMotorTorque(const WheelJoint& joint, Frequency inv_dt) noexcept
{
    return joint.GetAngularReaction() * inv_dt;
}
 
} // namespace d2
} // namespace playrho
 
#endif // PLAYRHO_DYNAMICS_JOINTS_WHEELJOINT_HPP