src/edu/berkeley/qfat/geom/Polygon.java

   1 package edu.berkeley.qfat.geom;
   2 import javax.media.opengl.*;
   3 import java.util.*;
   4 import edu.berkeley.qfat.Mesh;
   5
   6 // FIXME: numerical stability issues galore
   7 /** a planar, convex, possibly infinite/open polygon */
   8 public final class Polygon {
   9
  10     public final Plane plane;
  11
  12     private final HalfSpace[] halfSpaces;
  13
  14     public Polygon(Plane plane) { this(plane, new HalfSpace[0]); }
  15
  16     public Polygon(Plane plane, HalfSpace[] halfSpaces) {
  17         this.plane = plane;
  18         this.halfSpaces = halfSpaces;
  19     }
  20
  21     public Polygon intersect(HalfSpace hs) {
  22         HalfSpace[] newHalfSpaces = new HalfSpace[halfSpaces.length+1];
  23         System.arraycopy(halfSpaces, 0, newHalfSpaces, 0, halfSpaces.length);
  24         newHalfSpaces[newHalfSpaces.length-1] = hs;
  25         return new Polygon(plane, newHalfSpaces);
  26     }
  27
  28     public Triangle[] tesselate(Mesh mesh) {
  29         // FIXME: check for closedness
  30         // find a starting point
  31         HashSet<Segment> segments = new HashSet<Segment>();
  32         int i;
  33         for(i=0; i<halfSpaces.length; i++) {
  34             Point p1=null, p2=null;
  35             for(int j=0; j<halfSpaces.length; j++) {
  36                 if (i==j) continue;
  37                 Point p = plane.intersect(halfSpaces[i], halfSpaces[j]);
  38                 if (p==null) continue;
  39                 for(int k=0; k<halfSpaces.length; k++) {
  40                     if (i==k || j==k) continue;
  41                     //if (!halfSpaces[k].contains(p)) { p = null; break; }
  42                 }
  43                 if (p!=null) {
  44                     if (p1==null) p1 = p;
  45                     else if (p2==null) { if (!p.equals(p1)) p2 = p; }
  46                     else throw new Error();
  47                 }
  48             }
  49             if (p1!=null && p2!=null) {
  50                 System.out.println("new segment: " + p1 + " " + p2);
  51                 segments.add(new Segment(p1, p2));
  52             }
  53         }
  54         Vec cen = new Vec(0,0,0);
  55         for(Segment s : segments)
  56             cen = cen.plus(s.p1.minus(Point.ORIGIN)).plus(s.p2.minus(Point.ORIGIN));
  57         Point centroid = Point.ORIGIN.plus(cen.times(1f/(2*segments.size())));
  58         for(Segment s : segments) {
  59             System.out.println("newt! " + s.p1 + " " + centroid + " " + s.p2 + " " + plane.norm.times(-1));
  60             mesh.newT(s.p1, centroid, s.p2, plane.norm.times(-1), 0);
  61         }
  62         System.out.println("done");
  63         return null;
  64     }
  65
  66 }