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_GEAR_JOINT_H
 #define B2_GEAR_JOINT_H
 
 #include <Box2D/Dynamics/Joints/b2Joint.h>
 
 class b2RevoluteJoint;
 class b2PrismaticJoint;
 
 /// Gear joint definition. This definition requires two existing
 /// revolute or prismatic joints (any combination will work).
 /// The provided joints must attach a dynamic body to a static body.
 struct b2GearJointDef : public b2JointDef
 {
     b2GearJointDef()
     {
         type = e_gearJoint;
         joint1 = NULL;
         joint2 = NULL;
         ratio = 1.0f;
     }
 
     /// The first revolute/prismatic joint attached to the gear joint.
     b2Joint* joint1;
 
     /// The second revolute/prismatic joint attached to the gear joint.
     b2Joint* joint2;
 
     /// The gear ratio.
     /// @see b2GearJoint for explanation.
     qreal ratio;
 };
 
 /// A gear joint is used to connect two joints together. Either joint
 /// can be a revolute or prismatic joint. You specify a gear ratio
 /// to bind the motions together:
 /// coordinate1 + ratio * coordinate2 = constant
 /// The ratio can be negative or positive. If one joint is a revolute joint
 /// and the other joint is a prismatic joint, then the ratio will have units
 /// of length or units of 1/length.
 /// @warning The revolute and prismatic joints must be attached to
 /// fixed bodies (which must be body1 on those joints).
 class b2GearJoint : 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/Get the gear ratio.
     void SetRatio(qreal ratio);
     qreal GetRatio() const;
 
 protected:
 
     friend class b2Joint;
     b2GearJoint(const b2GearJointDef* data);
 
     void InitVelocityConstraints(const b2TimeStep& step) override;
     void SolveVelocityConstraints(const b2TimeStep& step) override;
     bool SolvePositionConstraints(qreal baumgarte) override;
 
     b2Body* m_ground1;
     b2Body* m_ground2;
 
     // One of these is NULL.
     b2RevoluteJoint* m_revolute1;
     b2PrismaticJoint* m_prismatic1;
 
     // One of these is NULL.
     b2RevoluteJoint* m_revolute2;
     b2PrismaticJoint* m_prismatic2;
 
     b2Vec2 m_groundAnchor1;
     b2Vec2 m_groundAnchor2;
 
     b2Vec2 m_localAnchor1;
     b2Vec2 m_localAnchor2;
 
     b2Jacobian m_J;
 
     qreal m_constant;
     qreal m_ratio;
 
     // Effective mass
     qreal m_mass;
 
     // Impulse for accumulation/warm starting.
     qreal m_impulse;
 };
 
 #endif