ContactID.java :  » Game » JBox2D-2.0.1 » org » jbox2d » collision » Java Open Source

/*
 * JBox2D - A Java Port of Erin Catto's Box2D
 * 
 * JBox2D homepage: http://jbox2d.sourceforge.net/ 
 * Box2D homepage: 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.
 */

package org.jbox2d.collision;

//Updated to rev 56->139 of b2Collision.h

//FIXME: In the C++ version, this class is a union of
//the key and the features, meaning not that it contains
//both separately, but that the same data can be accessed
//as either.  The key there is 32 bit, and each member of
//features is 8 bits.
//
//We need to figure out if this is a problem or not, because
//I have a feeling that as of right now, key is never being
//set anyways.  Initial examination seems to show that key is
//always zero. [hacked around for the moment]
//
//Also, it might be better performance-wise to pull features
//to a top level class if inner classes have more overhead (check this).
/** Contact ids to facilitate warm starting.*/
public class ContactID {
  /** Inactive in Java port (used for quick compares in C++ as part of a union) */
    public int key;

    /** The features that intersect to form the contact point */
    public Features features;
    
    /** The features that intersect to form the contact point */
    public class Features {
      /** The edge that defines the outward contact normal. */
        public int referenceEdge;
        /** The edge most anti-parallel to the reference edge. */
        public int incidentEdge;
        /** The vertex (0 or 1) on the incident edge that was clipped. */
        public int incidentVertex;
        /** A value of 1 indicates that the reference edge is on shape2. */
        public int flip;

        public Features() {
            referenceEdge = incidentEdge = incidentVertex = flip = 0;
        }

        public Features(Features f) {
            referenceEdge = f.referenceEdge;
            incidentEdge = f.incidentEdge;
            incidentVertex = f.incidentVertex;
            flip = f.flip;
        }
        
        public void set(Features f){
            referenceEdge = f.referenceEdge;
            incidentEdge = f.incidentEdge;
            incidentVertex = f.incidentVertex;
            flip = f.flip;
        }
        
        public boolean isEqual(Features f){
            return (referenceEdge==f.referenceEdge && 
                    incidentEdge==f.incidentEdge &&
                    incidentVertex==f.incidentVertex &&
                    flip==f.flip);
        }
        
        public String toString() {
          String s = "Features: (" + this.flip + " ," + this.incidentEdge + " ," + this.incidentVertex + " ," + this.referenceEdge + ")";
          return s;
        }

    }
    
    public boolean isEqual(ContactID cid) {
      return cid.features.isEqual(this.features);
    }
    
    public void zero() {
      key = 0;
      features.flip = 0;
      features.incidentEdge = 0;
      features.incidentVertex = 0;
      features.referenceEdge = 0;
    }

    public ContactID() {
        key = 0;
        features = new Features();
    }

    public ContactID(ContactID c) {
        key = c.key;
        features = new Features(c.features);
    }

}