115 lines
3.4 KiB
C++
115 lines
3.4 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_ROPE_JOINT_H
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#define B2_ROPE_JOINT_H
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#include "Box2D/Dynamics/Joints/b2Joint.h"
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/// Rope joint definition. This requires two body anchor points and
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/// a maximum lengths.
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/// Note: by default the connected objects will not collide.
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/// see collideConnected in b2JointDef.
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struct b2RopeJointDef : public b2JointDef
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{
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b2RopeJointDef()
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{
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type = e_ropeJoint;
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localAnchorA.Set(-1.0f, 0.0f);
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localAnchorB.Set(1.0f, 0.0f);
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maxLength = 0.0f;
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}
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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 maximum length of the rope.
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/// Warning: this must be larger than b2_linearSlop or
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/// the joint will have no effect.
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float32 maxLength;
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};
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/// A rope joint enforces a maximum distance between two points
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/// on two bodies. It has no other effect.
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/// Warning: if you attempt to change the maximum length during
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/// the simulation you will get some non-physical behavior.
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/// A model that would allow you to dynamically modify the length
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/// would have some sponginess, so I chose not to implement it
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/// that way. See b2DistanceJoint if you want to dynamically
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/// control length.
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class b2RopeJoint : 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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/// The local anchor point relative to bodyA's origin.
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const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
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/// The local anchor point relative to bodyB's origin.
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const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
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/// Set/Get the maximum length of the rope.
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void SetMaxLength(float32 length) { m_maxLength = length; }
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float32 GetMaxLength() const;
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b2LimitState GetLimitState() const;
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/// Dump joint to dmLog
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void Dump() override;
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protected:
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friend class b2Joint;
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b2RopeJoint(const b2RopeJointDef* 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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// Solver shared
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b2Vec2 m_localAnchorA;
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b2Vec2 m_localAnchorB;
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float32 m_maxLength;
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float32 m_length;
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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_u;
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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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b2LimitState m_state;
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};
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#endif
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