b2FrictionJoint.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_FRICTION_JOINT_H
- #define B2_FRICTION_JOINT_H
- #include <Box2D/Dynamics/Joints/b2Joint.h>
- /// Friction joint definition.
- struct b2FrictionJointDef : public b2JointDef
- {
- b2FrictionJointDef()
- {
- type = e_frictionJoint;
- localAnchorA.SetZero();
- localAnchorB.SetZero();
- maxForce = 0.0f;
- maxTorque = 0.0f;
- }
- /// Initialize the bodies, anchors, axis, and reference angle using the world
- /// anchor and world axis.
- void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
- /// The local anchor point relative to bodyA's origin.
- b2Vec2 localAnchorA;
- /// The local anchor point relative to bodyB's origin.
- b2Vec2 localAnchorB;
- /// The maximum friction force in N.
- float32 maxForce;
- /// The maximum friction torque in N-m.
- float32 maxTorque;
- };
- /// Friction joint. This is used for top-down friction.
- /// It provides 2D translational friction and angular friction.
- class b2FrictionJoint : public b2Joint
- {
- public:
- b2Vec2 GetAnchorA() const;
- b2Vec2 GetAnchorB() const;
- b2Vec2 GetReactionForce(float32 inv_dt) const;
- float32 GetReactionTorque(float32 inv_dt) const;
- /// Set the maximum friction force in N.
- void SetMaxForce(float32 force);
- /// Get the maximum friction force in N.
- float32 GetMaxForce() const;
- /// Set the maximum friction torque in N*m.
- void SetMaxTorque(float32 torque);
- /// Get the maximum friction torque in N*m.
- float32 GetMaxTorque() const;
- protected:
- friend class b2Joint;
- b2FrictionJoint(const b2FrictionJointDef* def);
- void InitVelocityConstraints(const b2TimeStep& step);
- void SolveVelocityConstraints(const b2TimeStep& step);
- bool SolvePositionConstraints(float32 baumgarte);
- b2Vec2 m_localAnchorA;
- b2Vec2 m_localAnchorB;
- b2Mat22 m_linearMass;
- float32 m_angularMass;
- b2Vec2 m_linearImpulse;
- float32 m_angularImpulse;
- float32 m_maxForce;
- float32 m_maxTorque;
- };
- #endif