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inc/Box2D/Dynamics/Joints/b2MotorJoint.h

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+/*
+* Copyright (c) 2006-2012 Erin Catto http://www.box2d.org
+*
+* 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_MOTOR_JOINT_H
+#define B2_MOTOR_JOINT_H
+
+#include <Box2D/Dynamics/Joints/b2Joint.h>
+
+/// Motor joint definition.
+struct b2MotorJointDef : public b2JointDef
+{
+	b2MotorJointDef()
+	{
+		type = e_motorJoint;
+		linearOffset.SetZero();
+		angularOffset = 0.0f;
+		maxForce = 1.0f;
+		maxTorque = 1.0f;
+		correctionFactor = 0.3f;
+	}
+
+	/// Initialize the bodies and offsets using the current transforms.
+	void Initialize(b2Body* bodyA, b2Body* bodyB);
+
+	/// Position of bodyB minus the position of bodyA, in bodyA's frame, in meters.
+	b2Vec2 linearOffset;
+
+	/// The bodyB angle minus bodyA angle in radians.
+	float32 angularOffset;
+	
+	/// The maximum motor force in N.
+	float32 maxForce;
+
+	/// The maximum motor torque in N-m.
+	float32 maxTorque;
+
+	/// Position correction factor in the range [0,1].
+	float32 correctionFactor;
+};
+
+/// A motor joint is used to control the relative motion
+/// between two bodies. A typical usage is to control the movement
+/// of a dynamic body with respect to the ground.
+class b2MotorJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Set/get the target linear offset, in frame A, in meters.
+	void SetLinearOffset(const b2Vec2& linearOffset);
+	const b2Vec2& GetLinearOffset() const;
+
+	/// Set/get the target angular offset, in radians.
+	void SetAngularOffset(float32 angularOffset);
+	float32 GetAngularOffset() 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;
+
+	/// Set the position correction factor in the range [0,1].
+	void SetCorrectionFactor(float32 factor);
+
+	/// Get the position correction factor in the range [0,1].
+	float32 GetCorrectionFactor() const;
+
+	/// Dump to b2Log
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+
+	b2MotorJoint(const b2MotorJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	// Solver shared
+	b2Vec2 m_linearOffset;
+	float32 m_angularOffset;
+	b2Vec2 m_linearImpulse;
+	float32 m_angularImpulse;
+	float32 m_maxForce;
+	float32 m_maxTorque;
+	float32 m_correctionFactor;
+
+	// Solver temp
+	int32 m_indexA;
+	int32 m_indexB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	b2Vec2 m_linearError;
+	float32 m_angularError;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Mat22 m_linearMass;
+	float32 m_angularMass;
+};
+
+#endif