mirror of https://github.com/axmolengine/axmol.git
112 lines
3.2 KiB
C++
112 lines
3.2 KiB
C++
/*
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* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef B2_GEAR_JOINT_H
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#define B2_GEAR_JOINT_H
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#include <Box2D/Dynamics/Joints/b2Joint.h>
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class b2RevoluteJoint;
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class b2PrismaticJoint;
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/// Gear joint definition. This definition requires two existing
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/// revolute or prismatic joints (any combination will work).
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/// The provided joints must attach a dynamic body to a static body.
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struct b2GearJointDef : public b2JointDef
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{
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b2GearJointDef()
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{
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type = e_gearJoint;
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joint1 = NULL;
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joint2 = NULL;
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ratio = 1.0f;
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}
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/// The first revolute/prismatic joint attached to the gear joint.
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b2Joint* joint1;
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/// The second revolute/prismatic joint attached to the gear joint.
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b2Joint* joint2;
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/// The gear ratio.
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/// @see b2GearJoint for explanation.
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float32 ratio;
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};
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/// A gear joint is used to connect two joints together. Either joint
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/// can be a revolute or prismatic joint. You specify a gear ratio
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/// to bind the motions together:
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/// coordinate1 + ratio * coordinate2 = constant
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/// The ratio can be negative or positive. If one joint is a revolute joint
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/// and the other joint is a prismatic joint, then the ratio will have units
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/// of length or units of 1/length.
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/// @warning The revolute and prismatic joints must be attached to
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/// fixed bodies (which must be body1 on those joints).
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class b2GearJoint : public b2Joint
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{
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public:
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b2Vec2 GetAnchorA() const;
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b2Vec2 GetAnchorB() const;
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b2Vec2 GetReactionForce(float32 inv_dt) const;
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float32 GetReactionTorque(float32 inv_dt) const;
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/// Set/Get the gear ratio.
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void SetRatio(float32 ratio);
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float32 GetRatio() const;
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protected:
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friend class b2Joint;
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b2GearJoint(const b2GearJointDef* data);
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void InitVelocityConstraints(const b2TimeStep& step);
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void SolveVelocityConstraints(const b2TimeStep& step);
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bool SolvePositionConstraints(float32 baumgarte);
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b2Body* m_ground1;
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b2Body* m_ground2;
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// One of these is NULL.
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b2RevoluteJoint* m_revolute1;
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b2PrismaticJoint* m_prismatic1;
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// One of these is NULL.
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b2RevoluteJoint* m_revolute2;
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b2PrismaticJoint* m_prismatic2;
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b2Vec2 m_groundAnchor1;
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b2Vec2 m_groundAnchor2;
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b2Vec2 m_localAnchor1;
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b2Vec2 m_localAnchor2;
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b2Jacobian m_J;
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float32 m_constant;
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float32 m_ratio;
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// Effective mass
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float32 m_mass;
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// Impulse for accumulation/warm starting.
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float32 m_impulse;
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};
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#endif
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