b2DistanceJoint.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_DISTANCE_JOINT_H
- #define B2_DISTANCE_JOINT_H
- #include <Box2D/Dynamics/Joints/b2Joint.h>
- /// Distance joint definition. This requires defining an
- /// anchor point on both bodies and the non-zero length of the
- /// distance joint. The definition uses local anchor points
- /// so that the initial configuration can violate the constraint
- /// slightly. This helps when saving and loading a game.
- /// @warning Do not use a zero or short length.
- struct b2DistanceJointDef : public b2JointDef
- {
- b2DistanceJointDef()
- {
- type = e_distanceJoint;
- localAnchorA.Set(0.0f, 0.0f);
- localAnchorB.Set(0.0f, 0.0f);
- length = 1.0f;
- frequencyHz = 0.0f;
- dampingRatio = 0.0f;
- }
- /// Initialize the bodies, anchors, and length using the world
- /// anchors.
- void Initialize(b2Body* bodyA, b2Body* bodyB,
- const b2Vec2& anchorA, const b2Vec2& anchorB);
- /// The local anchor point relative to body1's origin.
- b2Vec2 localAnchorA;
- /// The local anchor point relative to body2's origin.
- b2Vec2 localAnchorB;
- /// The natural length between the anchor points.
- float32 length;
- /// The mass-spring-damper frequency in Hertz.
- float32 frequencyHz;
- /// The damping ratio. 0 = no damping, 1 = critical damping.
- float32 dampingRatio;
- };
- /// A distance joint constrains two points on two bodies
- /// to remain at a fixed distance from each other. You can view
- /// this as a massless, rigid rod.
- class b2DistanceJoint : public b2Joint
- {
- public:
- b2Vec2 GetAnchorA() const;
- b2Vec2 GetAnchorB() const;
- b2Vec2 GetReactionForce(float32 inv_dt) const;
- float32 GetReactionTorque(float32 inv_dt) const;
- /// Set/get the natural length.
- /// Manipulating the length can lead to non-physical behavior when the frequency is zero.
- void SetLength(float32 length);
- float32 GetLength() const;
- // Set/get frequency in Hz.
- void SetFrequency(float32 hz);
- float32 GetFrequency() const;
- // Set/get damping ratio.
- void SetDampingRatio(float32 ratio);
- float32 GetDampingRatio() const;
- protected:
- friend class b2Joint;
- b2DistanceJoint(const b2DistanceJointDef* data);
- void InitVelocityConstraints(const b2TimeStep& step);
- void SolveVelocityConstraints(const b2TimeStep& step);
- bool SolvePositionConstraints(float32 baumgarte);
- b2Vec2 m_localAnchor1;
- b2Vec2 m_localAnchor2;
- b2Vec2 m_u;
- float32 m_frequencyHz;
- float32 m_dampingRatio;
- float32 m_gamma;
- float32 m_bias;
- float32 m_impulse;
- float32 m_mass;
- float32 m_length;
- };
- inline void b2DistanceJoint::SetLength(float32 length)
- {
- m_length = length;
- }
- inline float32 b2DistanceJoint::GetLength() const
- {
- return m_length;
- }
- inline void b2DistanceJoint::SetFrequency(float32 hz)
- {
- m_frequencyHz = hz;
- }
- inline float32 b2DistanceJoint::GetFrequency() const
- {
- return m_frequencyHz;
- }
- inline void b2DistanceJoint::SetDampingRatio(float32 ratio)
- {
- m_dampingRatio = ratio;
- }
- inline float32 b2DistanceJoint::GetDampingRatio() const
- {
- return m_dampingRatio;
- }
- #endif