File indexing completed on 2025-08-03 03:50:00

 /*
 * Copyright (c) 2006-2010 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_ROPE_JOINT_H
 #define B2_ROPE_JOINT_H
 
 #include <Box2D/Dynamics/Joints/b2Joint.h>
 
 /// Rope joint definition. This requires two body anchor points and
 /// a maximum lengths.
 /// Note: by default the connected objects will not collide.
 /// see collideConnected in b2JointDef.
 struct b2RopeJointDef : public b2JointDef
 {
     b2RopeJointDef()
     {
         type = e_ropeJoint;
         localAnchorA.Set(-1.0f, 0.0f);
         localAnchorB.Set(1.0f, 0.0f);
         maxLength = 0.0f;
     }
 
     /// The local anchor point relative to bodyA's origin.
     b2Vec2 localAnchorA;
 
     /// The local anchor point relative to bodyB's origin.
     b2Vec2 localAnchorB;
 
     /// The maximum length of the rope.
     /// Warning: this must be larger than b2_linearSlop or
     /// the joint will have no effect.
     qreal maxLength;
 };
 
 /// A rope joint enforces a maximum distance between two points
 /// on two bodies. It has no other effect.
 /// Warning: if you attempt to change the maximum length during
 /// the simulation you will get some non-physical behavior.
 /// A model that would allow you to dynamically modify the length
 /// would have some sponginess, so I chose not to implement it
 /// that way. See b2DistanceJoint if you want to dynamically
 /// control length.
 class b2RopeJoint : 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;
 
     /// Get the maximum length of the rope.
     qreal GetMaxLength() const;
 
     b2LimitState GetLimitState() const;
 
 protected:
 
     friend class b2Joint;
     b2RopeJoint(const b2RopeJointDef* data);
 
     void InitVelocityConstraints(const b2TimeStep& step) override;
     void SolveVelocityConstraints(const b2TimeStep& step) override;
     bool SolvePositionConstraints(qreal baumgarte) override;
 
     b2Vec2 m_localAnchorA;
     b2Vec2 m_localAnchorB;
 
     qreal m_maxLength;
     qreal m_length;
 
     // Jacobian info
     b2Vec2 m_u, m_rA, m_rB;
 
     // Effective mass
     qreal m_mass;
 
     // Impulses for accumulation/warm starting.
     qreal m_impulse;
 
     b2LimitState m_state;
 };
 
 #endif