initial commit. includes PhsyicsBox2dExtension

AndEngine/jni/Box2D/Dynamics/Joints/b2DistanceJoint.h

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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