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/*
* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
*
* 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_PRISMATIC_JOINT_H
#define B2_PRISMATIC_JOINT_H
#include "b2Joint.h"
/// Prismatic 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 b2PrismaticJointDef : public b2JointDef
{
b2PrismaticJointDef()
{
type = e_prismaticJoint;
localAnchor1.SetZero();
localAnchor2.SetZero();
localAxis1.Set(1.0f, 0.0f);
referenceAngle = 0.0f;
enableLimit = false;
lowerTranslation = 0.0f;
upperTranslation = 0.0f;
enableMotor = false;
maxMotorForce = 0.0f;
motorSpeed = 0.0f;
}
/// Initialize the bodies, anchors, axis, and reference angle using the world
/// anchor and world axis.
void Initialize(b2Body* body1, b2Body* body2, const b2Vec2& anchor, const b2Vec2& axis);
/// The local anchor point relative to body1's origin.
b2Vec2 localAnchor1;
/// The local anchor point relative to body2's origin.
b2Vec2 localAnchor2;
/// The local translation axis in body1.
b2Vec2 localAxis1;
/// The constrained angle between the bodies: body2_angle - body1_angle.
float32 referenceAngle;
/// Enable/disable the joint limit.
bool enableLimit;
/// The lower translation limit, usually in meters.
float32 lowerTranslation;
/// The upper translation limit, usually in meters.
float32 upperTranslation;
/// Enable/disable the joint motor.
bool enableMotor;
/// The maximum motor torque, usually in N-m.
float32 maxMotorForce;
/// The desired motor speed in radians per second.
float32 motorSpeed;
};
/// A prismatic joint. This joint provides one degree of freedom: translation
/// along an axis fixed in body1. Relative rotation is prevented. You can
/// use a joint limit to restrict the range of motion and a joint motor to
/// drive the motion or to model joint friction.
class b2PrismaticJoint : public b2Joint
{
public:
b2Vec2 GetAnchor1() const;
b2Vec2 GetAnchor2() const;
b2Vec2 GetReactionForce(float32 inv_dt) const;
float32 GetReactionTorque(float32 inv_dt) const;
/// Get the current joint translation, usually in meters.
float32 GetJointTranslation() const;
/// Get the current joint translation speed, usually in meters per second.
float32 GetJointSpeed() const;
/// Is the joint limit enabled?
bool IsLimitEnabled() const;
/// Enable/disable the joint limit.
void EnableLimit(bool flag);
/// Get the lower joint limit, usually in meters.
float32 GetLowerLimit() const;
/// Get the upper joint limit, usually in meters.
float32 GetUpperLimit() const;
/// Set the joint limits, usually in meters.
void SetLimits(float32 lower, float32 upper);
/// Is the joint motor enabled?
bool IsMotorEnabled() const;
/// Enable/disable the joint motor.
void EnableMotor(bool flag);
/// Set the motor speed, usually in meters per second.
void SetMotorSpeed(float32 speed);
/// Get the motor speed, usually in meters per second.
float32 GetMotorSpeed() const;
/// Set the maximum motor force, usually in N.
void SetMaxMotorForce(float32 force);
/// Get the current motor force, usually in N.
float32 GetMotorForce() const;
//--------------- Internals Below -------------------
b2PrismaticJoint(const b2PrismaticJointDef* def);
void InitVelocityConstraints(const b2TimeStep& step);
void SolveVelocityConstraints(const b2TimeStep& step);
bool SolvePositionConstraints(float32 baumgarte);
b2Vec2 m_localAnchor1;
b2Vec2 m_localAnchor2;
b2Vec2 m_localXAxis1;
b2Vec2 m_localYAxis1;
float32 m_refAngle;
b2Vec2 m_axis, m_perp;
float32 m_s1, m_s2;
float32 m_a1, m_a2;
b2Mat33 m_K;
b2Vec3 m_impulse;
float32 m_motorMass; // effective mass for motor/limit translational constraint.
float32 m_motorImpulse;
float32 m_lowerTranslation;
float32 m_upperTranslation;
float32 m_maxMotorForce;
float32 m_motorSpeed;
bool m_enableLimit;
bool m_enableMotor;
b2LimitState m_limitState;
};
inline float32 b2PrismaticJoint::GetMotorSpeed() const
{
return m_motorSpeed;
}
#endif
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