/* * Polygon2.java */package EDU.cmu.cs.coral.util; import java.io.*;import java.lang.*;import java.util.*;import EDU.gatech.cc.is.util.*;/** * A class for manipulating Polygon2s.   *  * <P> * <A HREF="../COPYRIGHT.html">Copyright</A> * (c)1998 Tucker Balch and Carnegie Mellon University * * @author Rosemary Emery * @version $Revision: 1.1 $  */public class Polygon2 implements Cloneable, Serializable	{	// vertices are stored in clockwise order	// edge zero runs from vertices[0] to vertices[1], edge one from vertices[1] to vertices[2]	// edge n from vertices[n] to vertices[0] where n is total number of edges	public Vector vertices = new Vector(); // a vector of Vec2s, each one implementing	public Polygon2()		{		vertices = new Vector();		}	public Polygon2(Vector vec)		{		vertices = new Vector();		for (int i=0;i<vec.size();i++)			{			vertices.addElement(vec.elementAt(i));			}		}	public Polygon2(Vec2 vertex)		{		vertices = new Vector();		vertices.addElement(vertex);		}	public Polygon2(Polygon2 p)		{		vertices = new Vector();		for (int i=0;i<p.vertices.size();i++)			{			vertices.addElement(p.vertices.elementAt(i));			}		}	/**	 * Create a new Polygon2 by cloning.	 * @param p Polygon2, the Polygon2 to copy.	 */	public 	Object clone()		{		return(new Polygon2(this));		}	/**	 * add a vertex to the Polygon2. 	 * @param vertex the new vertex.	 */	public void addVertex(Vec2 vertex)		{		vertices.addElement(vertex);		}	/**	 * return the ith vertex of the Polygon2. 	 * @param vertexNumber the ith vertex.	 */	public Vec2 returnVertex(int vertexNumber)		{		if (vertexNumber < vertices.size())			{			return (Vec2)vertices.elementAt(vertexNumber);			}		return null;		}	/**	 * translate the Polygon2 to a new origin 	 * @param offset, the new origin of the translated Polygon2       */	public void offsetVertices(Vec2 offset)		{		Vec2 temp;		for(int i=0;i<vertices.size();i++)			{			temp = (Vec2)vertices.elementAt(i);			temp.add(offset);			vertices.removeElementAt(i);			vertices.insertElementAt(temp, i);			}		}	public boolean pointWithinPolygon(Vec2 point)		{		int i = 0;		double outside;		Vec2 temp1, temp2;		boolean flag = true;		// assumes vertices given clockwise		while(i<vertices.size())			{			temp1 = (Vec2)vertices.elementAt(i);			temp2 = (Vec2)vertices.elementAt((i+1)%(vertices.size()));			outside = (point.y-temp1.y)*(temp2.x-temp1.x)-(point.x-temp1.x)*(temp2.y-temp1.y);			if (outside > 0) // point is to left of line (if on line stop)				{				flag = false;				break; 				}			i++;			}		return flag;		}	public boolean lineIntersectsWithPolygon(Vec2 vertex1, Vec2 vertex2)		{		int i=0;		Vec2 tempVec1, tempVec2;		Vec2 V1;		Vec2 V2 = new Vec2(vertex2.x-vertex1.x, vertex2.y-vertex1.y);		double t,s, denom;		while(i<vertices.size())			{			tempVec1 = (Vec2)vertices.elementAt(i);			tempVec2 = (Vec2)vertices.elementAt((i+1)%(vertices.size()));			V1 = new Vec2(tempVec2.x-tempVec1.x, tempVec2.y-tempVec1.y);			denom = -V1.x*V2.y + V1.y*V2.x;			t = (-1.0*V2.y*(vertex1.x - tempVec1.x) + V2.x*(vertex1.y-tempVec1.y))/denom;			s = (-1.0*V1.y*(vertex1.x-tempVec1.x) + V1.x*(vertex1.y-tempVec1.y))/denom;			if ((t > 0.005 && t < 0.995) && (s > 0.005 && s < 0.995))				{//				System.out.println("s t " + s + " " + t);//				System.out.println("t*vec 1 " + (t*V1.x + tempVec1.x) + " " + (t*V1.y + tempVec1.y));//				System.out.println("s*vec 2 " + (s*V2.x + vertex1.x) + " " + (s*V2.y + vertex1.y));				// as the intersection point is tV1 + tempVec1 t must lie between				// 0 and 1 in order for the intersection point to lie between tempVec1 and				// tempVec2				// similarly it is equal to sV2 + vertex1 and so s must lie between				// 0 and 1 in order for the intersection point to lie between vertex1				// and vertex 2, thus if both t and s are between these limits the				// intersection point is on the edge of the polygon and some form				// of collision (or just touching) is occuring				return true;				}			i++;			}		return false;		}	}