Joint.java

/*******************************************************************************
 * Copyright (c) 2011, Daniel Murphy
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the <organization> nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL DANIEL MURPHY BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ******************************************************************************/
package org.jbox2d.dynamics.joints;

import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.TimeStep;
import org.jbox2d.dynamics.World;
import org.jbox2d.pooling.WorldPool;

// updated to rev 100
/**
 * The base joint class. Joints are used to raint two bodies together in
 * various fashions. Some joints also feature limits and motors.
 * 
 * @author Daniel Murphy
 */
public abstract class Joint {
	
	public static Joint create(World argWorld, JointDef def) {
		//Joint joint = null;
		switch(def.type){
			case MOUSE:
				return new MouseJoint(argWorld.getPool(), (MouseJointDef) def);
			case DISTANCE:
				return new DistanceJoint(argWorld.getPool(), (DistanceJointDef) def);
			case PRISMATIC:
				return new PrismaticJoint(argWorld.getPool(), (PrismaticJointDef) def);
			case REVOLUTE:
				return new RevoluteJoint(argWorld.getPool(), (RevoluteJointDef) def);
			case WELD:
				return new WeldJoint(argWorld.getPool(), (WeldJointDef) def);
			case FRICTION:
				return new FrictionJoint(argWorld.getPool(), (FrictionJointDef) def);
			case LINE:
				return new LineJoint(argWorld.getPool(), (LineJointDef) def);
			case GEAR:
				return new GearJoint(argWorld.getPool(), (GearJointDef) def);
			case PULLEY:
				return new PulleyJoint(argWorld.getPool(), (PulleyJointDef) def);
			case CONSTANT_VOLUME:
				return new ConstantVolumeJoint(argWorld, (ConstantVolumeJointDef) def);
		}
		return null;
	}
	
	public static void destroy(Joint joint) {
		joint.destructor();
	}
	
	public JointType m_type;
	public Joint m_prev;
	public Joint m_next;
	public JointEdge m_edgeA;
	public JointEdge m_edgeB;
	public Body m_bodyA;
	public Body m_bodyB;
	
	public boolean m_islandFlag;
	public boolean m_collideConnected;
	
	public Object m_userData;
	
	protected WorldPool pool;
	
	// Cache here per time step to reduce cache misses.
	public final Vec2 m_localCenterA, m_localCenterB;
	float m_invMassA, m_invIA;
	float m_invMassB, m_invIB;
	
	protected Joint(WorldPool argWorldPool, JointDef def) {
		assert (def.bodyA != def.bodyB);
		
		pool = argWorldPool;
		m_type = def.type;
		m_prev = null;
		m_next = null;
		m_bodyA = def.bodyA;
		m_bodyB = def.bodyB;
		m_collideConnected = def.collideConnected;
		m_islandFlag = false;
		m_userData = def.userData;
		
		m_edgeA = new JointEdge();
		m_edgeA.joint = null;
		m_edgeA.other = null;
		m_edgeA.prev = null;
		m_edgeA.next = null;
		
		m_edgeB = new JointEdge();
		m_edgeB.joint = null;
		m_edgeB.other = null;
		m_edgeB.prev = null;
		m_edgeB.next = null;
		
		m_localCenterA = new Vec2();
		m_localCenterB = new Vec2();
	}
	
	/**
	 * get the type of the concrete joint.
	 * 
	 * @return
	 */
	public JointType getType() {
		return m_type;
	}
	
	/**
	 * get the first body attached to this joint.
	 */
	public Body getBodyA() {
		return m_bodyA;
	}
	
	/**
	 * get the second body attached to this joint.
	 * 
	 * @return
	 */
	public Body getBodyB() {
		return m_bodyB;
	}
	
	/**
	 * get the anchor point on bodyA in world coordinates.
	 * 
	 * @return
	 */
	public abstract void getAnchorA(Vec2 argOut);
	
	/**
	 * get the anchor point on bodyB in world coordinates.
	 * 
	 * @return
	 */
	public abstract void getAnchorB(Vec2 argOut);
	
	/**
	 * get the reaction force on body2 at the joint anchor in Newtons.
	 * 
	 * @param inv_dt
	 * @return
	 */
	public abstract void getReactionForce(float inv_dt, Vec2 argOut);
	
	/**
	 * get the reaction torque on body2 in N*m.
	 * 
	 * @param inv_dt
	 * @return
	 */
	public abstract float getReactionTorque(float inv_dt);
	
	/**
	 * get the next joint the world joint list.
	 */
	public Joint getNext() {
		return m_next;
	}
	
	/**
	 * get the user data pointer.
	 */
	public Object getUserData() {
		return m_userData;
	}
	
	/**
	 * Set the user data pointer.
	 */
	public void setUserData(Object data) {
		m_userData = data;
	}
	
	/**
	 * Short-cut function to determine if either body is inactive.
	 * 
	 * @return
	 */
	public boolean IsActive() {
		return m_bodyA.isActive() && m_bodyB.isActive();
	}
	
	public abstract void initVelocityConstraints(TimeStep step);
	
	public abstract void solveVelocityConstraints(TimeStep step);
	
	/**
	 * This returns true if the position errors are within tolerance.
	 * 
	 * @param baumgarte
	 * @return
	 */
	public abstract boolean solvePositionConstraints(float baumgarte);
	
	/**
	 * Override to handle destruction of joint
	 */
	public void destructor() { }
}