b2MouseJoint.h
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上传日期:2022-01-07
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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_MOUSE_JOINT_H
- #define B2_MOUSE_JOINT_H
- #include <Box2D/Dynamics/Joints/b2Joint.h>
- /// Mouse joint definition. This requires a world target point,
- /// tuning parameters, and the time step.
- struct b2MouseJointDef : public b2JointDef
- {
- b2MouseJointDef()
- {
- type = e_mouseJoint;
- target.Set(0.0f, 0.0f);
- maxForce = 0.0f;
- frequencyHz = 5.0f;
- dampingRatio = 0.7f;
- }
- /// The initial world target point. This is assumed
- /// to coincide with the body anchor initially.
- b2Vec2 target;
- /// The maximum constraint force that can be exerted
- /// to move the candidate body. Usually you will express
- /// as some multiple of the weight (multiplier * mass * gravity).
- float32 maxForce;
- /// The response speed.
- float32 frequencyHz;
- /// The damping ratio. 0 = no damping, 1 = critical damping.
- float32 dampingRatio;
- };
- /// A mouse joint is used to make a point on a body track a
- /// specified world point. This a soft constraint with a maximum
- /// force. This allows the constraint to stretch and without
- /// applying huge forces.
- /// NOTE: this joint is not documented in the manual because it was
- /// developed to be used in the testbed. If you want to learn how to
- /// use the mouse joint, look at the testbed.
- class b2MouseJoint : public b2Joint
- {
- public:
- /// Implements b2Joint.
- b2Vec2 GetAnchorA() const;
- /// Implements b2Joint.
- b2Vec2 GetAnchorB() const;
- /// Implements b2Joint.
- b2Vec2 GetReactionForce(float32 inv_dt) const;
- /// Implements b2Joint.
- float32 GetReactionTorque(float32 inv_dt) const;
- /// Use this to update the target point.
- void SetTarget(const b2Vec2& target);
- const b2Vec2& GetTarget() const;
- /// Set/get the maximum force in Newtons.
- void SetMaxForce(float32 force);
- float32 GetMaxForce() const;
- /// Set/get the frequency in Hertz.
- void SetFrequency(float32 hz);
- float32 GetFrequency() const;
- /// Set/get the damping ratio (dimensionless).
- void SetDampingRatio(float32 ratio);
- float32 GetDampingRatio() const;
- protected:
- friend class b2Joint;
- b2MouseJoint(const b2MouseJointDef* def);
- void InitVelocityConstraints(const b2TimeStep& step);
- void SolveVelocityConstraints(const b2TimeStep& step);
- bool SolvePositionConstraints(float32 baumgarte) { B2_NOT_USED(baumgarte); return true; }
- b2Vec2 m_localAnchor;
- b2Vec2 m_target;
- b2Vec2 m_impulse;
- b2Mat22 m_mass; // effective mass for point-to-point constraint.
- b2Vec2 m_C; // position error
- float32 m_maxForce;
- float32 m_frequencyHz;
- float32 m_dampingRatio;
- float32 m_beta;
- float32 m_gamma;
- };
- #endif