153 lines
4.4 KiB
C++
153 lines
4.4 KiB
C++
/*
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* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
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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_PULLEY_JOINT_H
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#define B2_PULLEY_JOINT_H
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#include "Box2D/Dynamics/Joints/b2Joint.h"
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const float32 b2_minPulleyLength = 2.0f;
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/// Pulley joint definition. This requires two ground anchors,
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/// two dynamic body anchor points, and a pulley ratio.
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struct b2PulleyJointDef : public b2JointDef
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{
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b2PulleyJointDef()
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{
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type = e_pulleyJoint;
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groundAnchorA.Set(-1.0f, 1.0f);
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groundAnchorB.Set(1.0f, 1.0f);
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localAnchorA.Set(-1.0f, 0.0f);
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localAnchorB.Set(1.0f, 0.0f);
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lengthA = 0.0f;
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lengthB = 0.0f;
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ratio = 1.0f;
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collideConnected = true;
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}
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/// Initialize the bodies, anchors, lengths, max lengths, and ratio using the world anchors.
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void Initialize(b2Body* bodyA, b2Body* bodyB,
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const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
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const b2Vec2& anchorA, const b2Vec2& anchorB,
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float32 ratio);
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/// The first ground anchor in world coordinates. This point never moves.
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b2Vec2 groundAnchorA;
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/// The second ground anchor in world coordinates. This point never moves.
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b2Vec2 groundAnchorB;
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/// The local anchor point relative to bodyA's origin.
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b2Vec2 localAnchorA;
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/// The local anchor point relative to bodyB's origin.
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b2Vec2 localAnchorB;
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/// The a reference length for the segment attached to bodyA.
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float32 lengthA;
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/// The a reference length for the segment attached to bodyB.
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float32 lengthB;
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/// The pulley ratio, used to simulate a block-and-tackle.
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float32 ratio;
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};
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/// The pulley joint is connected to two bodies and two fixed ground points.
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/// The pulley supports a ratio such that:
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/// length1 + ratio * length2 <= constant
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/// Yes, the force transmitted is scaled by the ratio.
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/// Warning: the pulley joint can get a bit squirrelly by itself. They often
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/// work better when combined with prismatic joints. You should also cover the
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/// the anchor points with static shapes to prevent one side from going to
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/// zero length.
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class b2PulleyJoint : public b2Joint
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{
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public:
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b2Vec2 GetAnchorA() const override;
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b2Vec2 GetAnchorB() const override;
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b2Vec2 GetReactionForce(float32 inv_dt) const override;
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float32 GetReactionTorque(float32 inv_dt) const override;
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/// Get the first ground anchor.
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b2Vec2 GetGroundAnchorA() const;
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/// Get the second ground anchor.
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b2Vec2 GetGroundAnchorB() const;
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/// Get the current length of the segment attached to bodyA.
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float32 GetLengthA() const;
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/// Get the current length of the segment attached to bodyB.
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float32 GetLengthB() const;
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/// Get the pulley ratio.
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float32 GetRatio() const;
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/// Get the current length of the segment attached to bodyA.
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float32 GetCurrentLengthA() const;
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/// Get the current length of the segment attached to bodyB.
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float32 GetCurrentLengthB() const;
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/// Dump joint to dmLog
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void Dump() override;
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/// Implement b2Joint::ShiftOrigin
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void ShiftOrigin(const b2Vec2& newOrigin) override;
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protected:
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friend class b2Joint;
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b2PulleyJoint(const b2PulleyJointDef* data);
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void InitVelocityConstraints(const b2SolverData& data) override;
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void SolveVelocityConstraints(const b2SolverData& data) override;
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bool SolvePositionConstraints(const b2SolverData& data) override;
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b2Vec2 m_groundAnchorA;
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b2Vec2 m_groundAnchorB;
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float32 m_lengthA;
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float32 m_lengthB;
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// Solver shared
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b2Vec2 m_localAnchorA;
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b2Vec2 m_localAnchorB;
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float32 m_constant;
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float32 m_ratio;
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float32 m_impulse;
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// Solver temp
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int32 m_indexA;
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int32 m_indexB;
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b2Vec2 m_uA;
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b2Vec2 m_uB;
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b2Vec2 m_rA;
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b2Vec2 m_rB;
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b2Vec2 m_localCenterA;
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b2Vec2 m_localCenterB;
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float32 m_invMassA;
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float32 m_invMassB;
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float32 m_invIA;
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float32 m_invIB;
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float32 m_mass;
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};
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#endif
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