File indexing completed on 2024-12-29 03:29:28

 /*
 * 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_WELD_JOINT_H
 #define B2_WELD_JOINT_H
 
 #include <Box2D/Dynamics/Joints/b2Joint.h>
 
 /// Weld joint definition. You need to specify local anchor points
 /// where they are attached and the relative body angle. The position
 /// of the anchor points is important for computing the reaction torque.
 struct b2WeldJointDef : public b2JointDef
 {
     b2WeldJointDef()
     {
         type = e_weldJoint;
         localAnchorA.Set(0.0f, 0.0f);
         localAnchorB.Set(0.0f, 0.0f);
         referenceAngle = 0.0f;
         frequencyHz = 0.0f;
         dampingRatio = 0.0f;
     }
 
     /// Initialize the bodies, anchors, and reference angle using a world
     /// anchor point.
     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 bodyB angle minus bodyA angle in the reference state (radians).
     float32 referenceAngle;
     
     /// The mass-spring-damper frequency in Hertz. Rotation only.
     /// Disable softness with a value of 0.
     float32 frequencyHz;
 
     /// The damping ratio. 0 = no damping, 1 = critical damping.
     float32 dampingRatio;
 };
 
 /// A weld joint essentially glues two bodies together. A weld joint may
 /// distort somewhat because the island constraint solver is approximate.
 class b2WeldJoint : public b2Joint
 {
 public:
     b2Vec2 GetAnchorA() const;
     b2Vec2 GetAnchorB() const;
 
     b2Vec2 GetReactionForce(float32 inv_dt) const;
     float32 GetReactionTorque(float32 inv_dt) const;
 
     /// 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; }
 
     /// Get the reference angle.
     float32 GetReferenceAngle() const { return m_referenceAngle; }
 
     /// Set/get frequency in Hz.
     void SetFrequency(float32 hz) { m_frequencyHz = hz; }
     float32 GetFrequency() const { return m_frequencyHz; }
 
     /// Set/get damping ratio.
     void SetDampingRatio(float32 ratio) { m_dampingRatio = ratio; }
     float32 GetDampingRatio() const { return m_dampingRatio; }
 
     /// Dump to b2Log
     void Dump();
 
 protected:
 
     friend class b2Joint;
 
     b2WeldJoint(const b2WeldJointDef* def);
 
     void InitVelocityConstraints(const b2SolverData& data);
     void SolveVelocityConstraints(const b2SolverData& data);
     bool SolvePositionConstraints(const b2SolverData& data);
 
     float32 m_frequencyHz;
     float32 m_dampingRatio;
     float32 m_bias;
 
     // Solver shared
     b2Vec2 m_localAnchorA;
     b2Vec2 m_localAnchorB;
     float32 m_referenceAngle;
     float32 m_gamma;
     b2Vec3 m_impulse;
 
     // Solver temp
     int32 m_indexA;
     int32 m_indexB;
     b2Vec2 m_rA;
     b2Vec2 m_rB;
     b2Vec2 m_localCenterA;
     b2Vec2 m_localCenterB;
     float32 m_invMassA;
     float32 m_invMassB;
     float32 m_invIA;
     float32 m_invIB;
     b2Mat33 m_mass;
 };
 
 #endif