b2PrismaticJoint.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_PRISMATIC_JOINT_H
- #define B2_PRISMATIC_JOINT_H
- #include <Box2D/Dynamics/Joints/b2Joint.h>
- /// Prismatic joint definition. This requires defining a line of
- /// motion using an axis and an anchor point. The definition uses local
- /// anchor points and a local axis so that the initial configuration
- /// can violate the constraint slightly. The joint translation is zero
- /// when the local anchor points coincide in world space. Using local
- /// anchors and a local axis helps when saving and loading a game.
- /// @warning at least one body should by dynamic with a non-fixed rotation.
- struct b2PrismaticJointDef : public b2JointDef
- {
- b2PrismaticJointDef()
- {
- type = e_prismaticJoint;
- localAnchorA.SetZero();
- localAnchorB.SetZero();
- localAxis1.Set(1.0f, 0.0f);
- referenceAngle = 0.0f;
- enableLimit = false;
- lowerTranslation = 0.0f;
- upperTranslation = 0.0f;
- enableMotor = false;
- maxMotorForce = 0.0f;
- motorSpeed = 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, const b2Vec2& axis);
- /// The local anchor point relative to body1's origin.
- b2Vec2 localAnchorA;
- /// The local anchor point relative to body2's origin.
- b2Vec2 localAnchorB;
- /// The local translation axis in body1.
- b2Vec2 localAxis1;
- /// The constrained angle between the bodies: body2_angle - body1_angle.
- float32 referenceAngle;
- /// Enable/disable the joint limit.
- bool enableLimit;
- /// The lower translation limit, usually in meters.
- float32 lowerTranslation;
- /// The upper translation limit, usually in meters.
- float32 upperTranslation;
- /// Enable/disable the joint motor.
- bool enableMotor;
- /// The maximum motor torque, usually in N-m.
- float32 maxMotorForce;
- /// The desired motor speed in radians per second.
- float32 motorSpeed;
- };
- /// A prismatic joint. This joint provides one degree of freedom: translation
- /// along an axis fixed in body1. Relative rotation is prevented. You can
- /// use a joint limit to restrict the range of motion and a joint motor to
- /// drive the motion or to model joint friction.
- class b2PrismaticJoint : public b2Joint
- {
- public:
- b2Vec2 GetAnchorA() const;
- b2Vec2 GetAnchorB() const;
- b2Vec2 GetReactionForce(float32 inv_dt) const;
- float32 GetReactionTorque(float32 inv_dt) const;
- /// Get the current joint translation, usually in meters.
- float32 GetJointTranslation() const;
- /// Get the current joint translation speed, usually in meters per second.
- float32 GetJointSpeed() const;
- /// Is the joint limit enabled?
- bool IsLimitEnabled() const;
- /// Enable/disable the joint limit.
- void EnableLimit(bool flag);
- /// Get the lower joint limit, usually in meters.
- float32 GetLowerLimit() const;
- /// Get the upper joint limit, usually in meters.
- float32 GetUpperLimit() const;
- /// Set the joint limits, usually in meters.
- void SetLimits(float32 lower, float32 upper);
- /// Is the joint motor enabled?
- bool IsMotorEnabled() const;
- /// Enable/disable the joint motor.
- void EnableMotor(bool flag);
- /// Set the motor speed, usually in meters per second.
- void SetMotorSpeed(float32 speed);
- /// Get the motor speed, usually in meters per second.
- float32 GetMotorSpeed() const;
- /// Set the maximum motor force, usually in N.
- void SetMaxMotorForce(float32 force);
- /// Get the current motor force, usually in N.
- float32 GetMotorForce() const;
- protected:
- friend class b2Joint;
- friend class b2GearJoint;
- b2PrismaticJoint(const b2PrismaticJointDef* def);
- void InitVelocityConstraints(const b2TimeStep& step);
- void SolveVelocityConstraints(const b2TimeStep& step);
- bool SolvePositionConstraints(float32 baumgarte);
- b2Vec2 m_localAnchor1;
- b2Vec2 m_localAnchor2;
- b2Vec2 m_localXAxis1;
- b2Vec2 m_localYAxis1;
- float32 m_refAngle;
- b2Vec2 m_axis, m_perp;
- float32 m_s1, m_s2;
- float32 m_a1, m_a2;
- b2Mat33 m_K;
- b2Vec3 m_impulse;
- float32 m_motorMass; // effective mass for motor/limit translational constraint.
- float32 m_motorImpulse;
- float32 m_lowerTranslation;
- float32 m_upperTranslation;
- float32 m_maxMotorForce;
- float32 m_motorSpeed;
-
- bool m_enableLimit;
- bool m_enableMotor;
- b2LimitState m_limitState;
- };
- inline float32 b2PrismaticJoint::GetMotorSpeed() const
- {
- return m_motorSpeed;
- }
- #endif