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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_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.
- float32 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;
- b2Vec2 GetAnchorB() const;
- b2Vec2 GetReactionForce(float32 inv_dt) const;
- float32 GetReactionTorque(float32 inv_dt) const;
- /// Set/Get the gear ratio.
- void SetRatio(float32 ratio);
- float32 GetRatio() const;
- protected:
- friend class b2Joint;
- b2GearJoint(const b2GearJointDef* data);
- void InitVelocityConstraints(const b2TimeStep& step);
- void SolveVelocityConstraints(const b2TimeStep& step);
- bool SolvePositionConstraints(float32 baumgarte);
- 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;
- float32 m_constant;
- float32 m_ratio;
- // Effective mass
- float32 m_mass;
- // Impulse for accumulation/warm starting.
- float32 m_impulse;
- };
- #endif
