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/*
* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
*
* 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 B2_WHEEL_JOINT_H
#define B2_WHEEL_JOINT_H
#include "Box2D/Dynamics/Joints/b2Joint.h"
/// Wheel joint definition. This requires defining a line of
/// motion using an axis and an anchor point. The definition uses local
/// anchor points and a local axis so that the initial configuration
/// can violate the constraint slightly. The joint translation is zero
/// when the local anchor points coincide in world space. Using local
/// anchors and a local axis helps when saving and loading a game.
struct b2WheelJointDef : public b2JointDef
{
b2WheelJointDef()
{
type = e_wheelJoint;
localAnchorA.SetZero();
localAnchorB.SetZero();
localAxisA.Set(1.0f, 0.0f);
enableMotor = false;
maxMotorTorque = 0.0f;
motorSpeed = 0.0f;
frequencyHz = 2.0f;
dampingRatio = 0.7f;
}
/// Initialize the bodies, anchors, axis, and reference angle using the world
/// anchor and world axis.
void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);
/// The local anchor point relative to bodyA's origin.
b2Vec2 localAnchorA;
/// The local anchor point relative to bodyB's origin.
b2Vec2 localAnchorB;
/// The local translation axis in bodyA.
b2Vec2 localAxisA;
/// Enable/disable the joint motor.
bool enableMotor;
/// The maximum motor torque, usually in N-m.
float32 maxMotorTorque;
/// The desired motor speed in radians per second.
float32 motorSpeed;
/// Suspension frequency, zero indicates no suspension
float32 frequencyHz;
/// Suspension damping ratio, one indicates critical damping
float32 dampingRatio;
};
/// A wheel joint. This joint provides two degrees of freedom: translation
/// along an axis fixed in bodyA and rotation in the plane. In other words, it is a point to
/// line constraint with a rotational motor and a linear spring/damper.
/// This joint is designed for vehicle suspensions.
class b2WheelJoint : public b2Joint
{
public:
b2Vec2 GetAnchorA() const override;
b2Vec2 GetAnchorB() const override;
b2Vec2 GetReactionForce(float32 inv_dt) const override;
float32 GetReactionTorque(float32 inv_dt) const override;
/// The local anchor point relative to bodyA's origin.
const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
/// The local anchor point relative to bodyB's origin.
const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
/// The local joint axis relative to bodyA.
const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; }
/// Get the current joint translation, usually in meters.
float32 GetJointTranslation() const;
/// Get the current joint linear speed, usually in meters per second.
float32 GetJointLinearSpeed() const;
/// Get the current joint angle in radians.
float32 GetJointAngle() const;
/// Get the current joint angular speed in radians per second.
float32 GetJointAngularSpeed() const;
/// Is the joint motor enabled?
bool IsMotorEnabled() const;
/// Enable/disable the joint motor.
void EnableMotor(bool flag);
/// Set the motor speed, usually in radians per second.
void SetMotorSpeed(float32 speed);
/// Get the motor speed, usually in radians per second.
float32 GetMotorSpeed() const;
/// Set/Get the maximum motor force, usually in N-m.
void SetMaxMotorTorque(float32 torque);
float32 GetMaxMotorTorque() const;
/// Get the current motor torque given the inverse time step, usually in N-m.
float32 GetMotorTorque(float32 inv_dt) const;
/// Set/Get the spring frequency in hertz. Setting the frequency to zero disables the spring.
void SetSpringFrequencyHz(float32 hz);
float32 GetSpringFrequencyHz() const;
/// Set/Get the spring damping ratio
void SetSpringDampingRatio(float32 ratio);
float32 GetSpringDampingRatio() const;
/// Dump to b2Log
void Dump() 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;
float32 m_frequencyHz;
float32 m_dampingRatio;
// Solver shared
b2Vec2 m_localAnchorA;
b2Vec2 m_localAnchorB;
b2Vec2 m_localXAxisA;
b2Vec2 m_localYAxisA;
float32 m_impulse;
float32 m_motorImpulse;
float32 m_springImpulse;
float32 m_maxMotorTorque;
float32 m_motorSpeed;
bool m_enableMotor;
// Solver temp
int32 m_indexA;
int32 m_indexB;
b2Vec2 m_localCenterA;
b2Vec2 m_localCenterB;
float32 m_invMassA;
float32 m_invMassB;
float32 m_invIA;
float32 m_invIB;
b2Vec2 m_ax, m_ay;
float32 m_sAx, m_sBx;
float32 m_sAy, m_sBy;
float32 m_mass;
float32 m_motorMass;
float32 m_springMass;
float32 m_bias;
float32 m_gamma;
};
inline float32 b2WheelJoint::GetMotorSpeed() const
{
return m_motorSpeed;
}
inline float32 b2WheelJoint::GetMaxMotorTorque() const
{
return m_maxMotorTorque;
}
inline void b2WheelJoint::SetSpringFrequencyHz(float32 hz)
{
m_frequencyHz = hz;
}
inline float32 b2WheelJoint::GetSpringFrequencyHz() const
{
return m_frequencyHz;
}
inline void b2WheelJoint::SetSpringDampingRatio(float32 ratio)
{
m_dampingRatio = ratio;
}
inline float32 b2WheelJoint::GetSpringDampingRatio() const
{
return m_dampingRatio;
}
#endif
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