File indexing completed on 2025-08-03 03:49:58

 /*
 * 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_FRICTION_JOINT_H
 #define B2_FRICTION_JOINT_H
 
 #include <Box2D/Dynamics/Joints/b2Joint.h>
 
 /// Friction joint definition.
 struct b2FrictionJointDef : public b2JointDef
 {
     b2FrictionJointDef()
     {
         type = e_frictionJoint;
         localAnchorA.SetZero();
         localAnchorB.SetZero();
         maxForce = 0.0f;
         maxTorque = 0.0f;
     }
 
     /// Initialize the bodies, anchors, axis, and reference angle using the world
     /// anchor and world axis.
     void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
 
     /// The local anchor point relative to bodyA's origin.
     b2Vec2 localAnchorA;
 
     /// The local anchor point relative to bodyB's origin.
     b2Vec2 localAnchorB;
 
     /// The maximum friction force in N.
     qreal maxForce;
 
     /// The maximum friction torque in N-m.
     qreal maxTorque;
 };
 
 /// Friction joint. This is used for top-down friction.
 /// It provides 2D translational friction and angular friction.
 class b2FrictionJoint : public b2Joint
 {
 public:
     b2Vec2 GetAnchorA() const override;
     b2Vec2 GetAnchorB() const override;
 
     b2Vec2 GetReactionForce(qreal inv_dt) const override;
     qreal GetReactionTorque(qreal inv_dt) const override;
 
     /// Set the maximum friction force in N.
     void SetMaxForce(qreal force);
 
     /// Get the maximum friction force in N.
     qreal GetMaxForce() const;
 
     /// Set the maximum friction torque in N*m.
     void SetMaxTorque(qreal torque);
 
     /// Get the maximum friction torque in N*m.
     qreal GetMaxTorque() const;
 
 protected:
 
     friend class b2Joint;
 
     b2FrictionJoint(const b2FrictionJointDef* def);
 
     void InitVelocityConstraints(const b2TimeStep& step) override;
     void SolveVelocityConstraints(const b2TimeStep& step) override;
     bool SolvePositionConstraints(qreal baumgarte) override;
 
     b2Vec2 m_localAnchorA;
     b2Vec2 m_localAnchorB;
 
     b2Mat22 m_linearMass;
     qreal m_angularMass;
 
     b2Vec2 m_linearImpulse;
     qreal m_angularImpulse;
 
     qreal m_maxForce;
     qreal m_maxTorque;
 };
 
 #endif