130 lines
3.7 KiB
C++
130 lines
3.7 KiB
C++
/*
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* Copyright (c) 2006-2007 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_MOUSE_JOINT_H
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#define B2_MOUSE_JOINT_H
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#include "Box2D/Dynamics/Joints/b2Joint.h"
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/// Mouse joint definition. This requires a world target point,
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/// tuning parameters, and the time step.
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struct b2MouseJointDef : public b2JointDef
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{
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b2MouseJointDef()
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{
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type = e_mouseJoint;
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target.Set(0.0f, 0.0f);
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maxForce = 0.0f;
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frequencyHz = 5.0f;
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dampingRatio = 0.7f;
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}
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/// The initial world target point. This is assumed
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/// to coincide with the body anchor initially.
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b2Vec2 target;
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/// The maximum constraint force that can be exerted
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/// to move the candidate body. Usually you will express
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/// as some multiple of the weight (multiplier * mass * gravity).
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float32 maxForce;
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/// The response speed.
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float32 frequencyHz;
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/// The damping ratio. 0 = no damping, 1 = critical damping.
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float32 dampingRatio;
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};
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/// A mouse joint is used to make a point on a body track a
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/// specified world point. This a soft constraint with a maximum
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/// force. This allows the constraint to stretch and without
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/// applying huge forces.
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/// NOTE: this joint is not documented in the manual because it was
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/// developed to be used in the testbed. If you want to learn how to
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/// use the mouse joint, look at the testbed.
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class b2MouseJoint : public b2Joint
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{
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public:
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/// Implements b2Joint.
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b2Vec2 GetAnchorA() const override;
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/// Implements b2Joint.
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b2Vec2 GetAnchorB() const override;
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/// Implements b2Joint.
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b2Vec2 GetReactionForce(float32 inv_dt) const override;
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/// Implements b2Joint.
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float32 GetReactionTorque(float32 inv_dt) const override;
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/// Use this to update the target point.
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void SetTarget(const b2Vec2& target);
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const b2Vec2& GetTarget() const;
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/// Set/get the maximum force in Newtons.
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void SetMaxForce(float32 force);
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float32 GetMaxForce() const;
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/// Set/get the frequency in Hertz.
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void SetFrequency(float32 hz);
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float32 GetFrequency() const;
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/// Set/get the damping ratio (dimensionless).
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void SetDampingRatio(float32 ratio);
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float32 GetDampingRatio() const;
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/// The mouse joint does not support dumping.
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void Dump() override { b2Log("Mouse joint dumping is not supported.\n"); }
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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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b2MouseJoint(const b2MouseJointDef* def);
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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_localAnchorB;
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b2Vec2 m_targetA;
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float32 m_frequencyHz;
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float32 m_dampingRatio;
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float32 m_beta;
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// Solver shared
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b2Vec2 m_impulse;
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float32 m_maxForce;
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float32 m_gamma;
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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_rB;
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b2Vec2 m_localCenterB;
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float32 m_invMassB;
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float32 m_invIB;
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b2Mat22 m_mass;
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b2Vec2 m_C;
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};
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#endif
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