initial commit. includes PhsyicsBox2dExtension

AndEngine/jni/Box2D/Dynamics/Joints/b2PulleyJoint.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_PULLEY_JOINT_H
+#define B2_PULLEY_JOINT_H
+
+#include "Box2D/Dynamics/Joints/b2Joint.h"
+
+const float32 b2_minPulleyLength = 2.0f;
+
+/// Pulley joint definition. This requires two ground anchors,
+/// two dynamic body anchor points, max lengths for each side,
+/// and a pulley ratio.
+struct b2PulleyJointDef : public b2JointDef
+{
+	b2PulleyJointDef()
+	{
+		type = e_pulleyJoint;
+		groundAnchorA.Set(-1.0f, 1.0f);
+		groundAnchorB.Set(1.0f, 1.0f);
+		localAnchorA.Set(-1.0f, 0.0f);
+		localAnchorB.Set(1.0f, 0.0f);
+		lengthA = 0.0f;
+		maxLengthA = 0.0f;
+		lengthB = 0.0f;
+		maxLengthB = 0.0f;
+		ratio = 1.0f;
+		collideConnected = true;
+	}
+
+	/// Initialize the bodies, anchors, lengths, max lengths, and ratio using the world anchors.
+	void Initialize(b2Body* bodyA, b2Body* bodyB,
+					const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
+					const b2Vec2& anchorA, const b2Vec2& anchorB,
+					float32 ratio);
+
+	/// The first ground anchor in world coordinates. This point never moves.
+	b2Vec2 groundAnchorA;
+
+	/// The second ground anchor in world coordinates. This point never moves.
+	b2Vec2 groundAnchorB;
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The a reference length for the segment attached to bodyA.
+	float32 lengthA;
+
+	/// The maximum length of the segment attached to bodyA.
+	float32 maxLengthA;
+
+	/// The a reference length for the segment attached to bodyB.
+	float32 lengthB;
+
+	/// The maximum length of the segment attached to bodyB.
+	float32 maxLengthB;
+
+	/// The pulley ratio, used to simulate a block-and-tackle.
+	float32 ratio;
+};
+
+/// The pulley joint is connected to two bodies and two fixed ground points.
+/// The pulley supports a ratio such that:
+/// length1 + ratio * length2 <= constant
+/// Yes, the force transmitted is scaled by the ratio.
+/// The pulley also enforces a maximum length limit on both sides. This is
+/// useful to prevent one side of the pulley hitting the top.
+class b2PulleyJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Get the first ground anchor.
+	b2Vec2 GetGroundAnchorA() const;
+
+	/// Get the second ground anchor.
+	b2Vec2 GetGroundAnchorB() const;
+
+	/// Get the current length of the segment attached to body1.
+	float32 GetLength1() const;
+
+	/// Get the current length of the segment attached to body2.
+	float32 GetLength2() const;
+
+	/// Get the pulley ratio.
+	float32 GetRatio() const;
+
+protected:
+
+	friend class b2Joint;
+	b2PulleyJoint(const b2PulleyJointDef* data);
+
+	void InitVelocityConstraints(const b2TimeStep& step);
+	void SolveVelocityConstraints(const b2TimeStep& step);
+	bool SolvePositionConstraints(float32 baumgarte);
+
+	b2Vec2 m_groundAnchor1;
+	b2Vec2 m_groundAnchor2;
+	b2Vec2 m_localAnchor1;
+	b2Vec2 m_localAnchor2;
+
+	b2Vec2 m_u1;
+	b2Vec2 m_u2;
+	
+	float32 m_constant;
+	float32 m_ratio;
+	
+	float32 m_maxLength1;
+	float32 m_maxLength2;
+
+	// Effective masses
+	float32 m_pulleyMass;
+	float32 m_limitMass1;
+	float32 m_limitMass2;
+
+	// Impulses for accumulation/warm starting.
+	float32 m_impulse;
+	float32 m_limitImpulse1;
+	float32 m_limitImpulse2;
+
+	b2LimitState m_state;
+	b2LimitState m_limitState1;
+	b2LimitState m_limitState2;
+};
+
+#endif