bug hunting

src/org/poly2tri/MonoToneMountain.scala

@@ -32,6 +32,7 @@ package org.poly2tri
 
 import scala.collection.mutable.{ArrayBuffer, Queue}
 
+// Doubly linked list
 class MonotoneMountain {
 
 	var tail, head: Point = null
@@ -40,7 +41,7 @@ class MonotoneMountain {
 	val convexPoints = new Queue[Point]
 	val triangles = new ArrayBuffer[Array[Point]]
  
-	// Append
+	// Append a point to the list
 	def +=(point: Point) {
 	  size match {
 	    case 0 => 
@@ -57,8 +58,8 @@ class MonotoneMountain {
 	  size += 1
 	}
 
-	// Remove
+	// Remove a point from the list
-	private def remove(point: Point) {
+	def remove(point: Point) {
 		val next = point.next
 		val prev = point.prev
 		point.prev.next = next
@@ -66,16 +67,66 @@ class MonotoneMountain {
 		size -= 1
 	}
  
-	// Determines if the inslide angle between edge v2-v3 and edge v2-v1 is convex (< PI)
+	// Partition a x-monotone mountain into triangles O(n)
-	private def angle(v1: Point, v2: Point, v3: Point) = {
+	// See "Computational Geometry in C", 2nd edition, by Joseph O'Rourke, page 52
-	  val a = (v2 - v1) 
+	def triangulate {
-	  val b = (v2 - v3) 
+		
-      val angle = Math.atan2(b.y,b.x).toFloat - Math.atan2(a.y,a.x).toFloat
+	  if(size == 3) {
-      angle
+	    lastTriangle
+	  } else {
+	   // Initialize internal angles at each nonbase vertex
+	   var p = head.next
+	   while(p != tail) {
+	     // Link strictly convex vertices into a list
+	     if(convex(p)) convexPoints.enqueue(p)
+	     p = p.next
+	   }
+    
+	   while(!convexPoints.isEmpty) {
+	     
+	     val ear = convexPoints.dequeue
+	     val a = ear.prev.clone
+	     val b = ear
+	     val c = ear.next.clone
+	     val triangle = Array(a, b, c)
+	     triangles += triangle
+	     
+	     // Remove ear, update angles and convex list
+	     remove(ear) 
+	     if(a.prev != null && convex(a)) convexPoints.enqueue(a); 
+         if(c.prev != null && convex(c)) convexPoints.enqueue(c)
+
+	   }
+	   if(size == 3)lastTriangle
+	}
+   }
+ 
+	// Return the monotone polygon 
+	def monoPoly: Array[Point] = {
+	  val poly = new Array[Point](size)
+	  var i = 0
+      var p = head
+	  while(p != null) {
+	      poly(i) = p
+	      p = p.next
+          i += 1
+	  }
+	  poly
+	}
+ 
+	// Determines if the inslide angle between edge v2-v3 and edge v2-v1 is convex 
+	private def convex(p: Point) = {
+	  val a = (p.next - p) 
+	  val b = (p.prev - p) 
+      var angle = Math.atan2(b.y,b.x).toFloat - Math.atan2(a.y,a.x).toFloat
+      if(p.y >= head.y) {
+        (angle < 0)
+      } else {
+        !(angle < 0)
+      }
     }
 
-	def lastTriangle = {
+	private def lastTriangle {
-	  assert(size == 3, "Number of points = " + size)
 	  val triangle = new Array[Point](3)
 	  var i = 0
       var p = head
@@ -86,53 +137,4 @@ class MonotoneMountain {
 	  }
 	  triangles += triangle
 	}
- 
-	// Partition a x-monotone mountain into triangles o(n)
-	// See "Computational Geometry in C", 2nd edition, by Joseph O'Rourke, page 52
-	def triangulate {
-	  if(size == 3) {
-	    lastTriangle
-	  } else {
-	   // Initialize internal angles at each nonbase vertex
-	   var p = head.next
-	   while(p != tail) {
-	     p.angle = Math.abs(angle(p.prev, p, p.next))
-	     println("angle = " + p.angle)
-	     // Link strictly convex vertices into a list
-	     if(p.angle >= 0 && p.angle <= Math.Pi) convexPoints.enqueue(p)
-	     p = p.next
-	   }
-    
-	   while(!convexPoints.isEmpty) {
-	     val ear = convexPoints.dequeue
-	     val a = ear.prev.clone
-	     val b = ear
-	     val c = ear.next.clone
-	     val triangle = Array(a, b, c)
-	     triangles += triangle
-      
-	     // Remove ear, update angles and convex list
-	     remove(ear) 
-	     a.angle -= ear.angle
-	     if(a.angle > 0 && a != head && a != tail) convexPoints.enqueue(a)
-	     c.angle -= ear.angle
-	     if(c.angle > 0 && c != head && c != tail) convexPoints.enqueue(c)
-	   }
-    
-	   if(size > 2)lastTriangle
-	}
-   }
- 
-	def monoPoly {
-	  val triangle = new Array[Point](size)
-	  var i = 0
-      var p = head
-	  while(p != null) {
-	      triangle(i) = p
-	      p = p.next
-          i += 1
-	  }
-	  triangles += triangle
-	  println(size)
-	}
 }

src/org/poly2tri/Poly2Tri.scala

@@ -61,8 +61,10 @@ class Poly2TriDemo extends BasicGame("Poly2Tri") {
   var drawMap = false
   
   def init(container: GameContainer) {
-    testTesselator
+    // TODO: Add text file point loader
-    //snake
+    //poly
+    //poly2
+    snake
   }
   
   def update(gc: GameContainer, delta: Int) {
@@ -92,14 +94,19 @@ class Poly2TriDemo extends BasicGame("Poly2Tri") {
 	    }
    }
    
+    var i = 0
     for(x <- tesselator.xMonoPoly) {
       var t = x.triangles
+      var j = 0
       for(t <- x.triangles) { 
         val triangle = new Polygon()
         t.foreach(p => triangle.addPoint(p.x, p.y))
-        g.setColor(green)
+        val color = if(i == 0 && j == 3) blue else green
+        g.setColor(color)
         g.draw(triangle)
+        j += 1
       }
+      i += 1
     }
   }
   
@@ -109,7 +116,8 @@ class Poly2TriDemo extends BasicGame("Poly2Tri") {
     if(c == 'm') drawMap = !drawMap
   }
   
-  def testTesselator {
+  // Test #1
+  def poly {
    
     val scale = 1.0f
     val p1 = new Point(100,300)*scale
@@ -131,6 +139,37 @@ class Poly2TriDemo extends BasicGame("Poly2Tri") {
     tesselator.process
    }
   
+  def poly2 {
+
+	val scale = 1.0f
+    val displace = 0f
+    val p1 = new Point(350,75)*scale+displace
+    val p2 = new Point(379,161)*scale+displace
+    val p3 = new Point(469,161)*scale+displace
+    val p4 = new Point(397,215)*scale+displace
+    val p5 = new Point(423,301)*scale+displace
+    val p6 = new Point(350,250)*scale+displace
+    val p7 = new Point(277,301)*scale+displace
+    val p8 = new Point(303,215)*scale+displace
+    val p9 = new Point(231,161)*scale+displace
+    val p10 = new Point(321,161)*scale+displace
+    
+    val segments = new ArrayList[Segment]
+    segments += new Segment(p1, p2)
+    segments += new Segment(p2, p3)
+    segments += new Segment(p3, p4)
+    segments += new Segment(p4, p5)
+    segments += new Segment(p5, p6)
+    segments += new Segment(p6, p7) 
+    segments += new Segment(p7, p8)
+    segments += new Segment(p8, p9)
+    segments += new Segment(p9, p10)
+    segments += new Segment(p10, p1)
+    tesselator = new Triangulator(segments)
+    tesselator.process
+  }
+  
+  // Test #2
   def snake {
 
     val scale = 10.0f

src/org/poly2tri/Segment.scala

@@ -40,7 +40,8 @@ class Segment(var p: Point, var q: Point) {
   var above, below, left: Trapezoid = null
   
   // Montone mountain points
-  val mPoints = HashSet(p, q)
+  // Use a HashSet to avoid repeats
+  val mPoints = HashSet.empty[Point]
   
   // Equation of a line: y = m*x + b
   // Slope of the line (m)

src/org/poly2tri/Sink.scala

@@ -39,7 +39,6 @@ object Sink {
       new Sink(trapezoid)
     }
   }
-  
 }
 
 class Sink(val trapezoid: Trapezoid) extends Node(null, null) {

src/org/poly2tri/Trapezoid.scala

@@ -82,11 +82,10 @@ class Trapezoid(val leftPoint: Point, var rightPoint: Point, val top: Segment, v
   } 
   
   // Add points to monotone mountain
-  // Use HashSet to aboid repeats
   def mark {
-    bottom.mPoints += leftPoint
+    if(leftPoint != bottom.p) bottom.mPoints += leftPoint
-    bottom.mPoints += rightPoint
+    if(rightPoint != bottom.q) bottom.mPoints += rightPoint
-    top.mPoints += leftPoint
+    if(leftPoint != top.p) top.mPoints += leftPoint
-    top.mPoints += rightPoint
+    if(rightPoint != top.q) top.mPoints += rightPoint
   }
 }

src/org/poly2tri/Triangulator.scala

@@ -93,15 +93,11 @@ class Triangulator(var segments: ArrayList[Segment]) {
   // Build a list of x-monotone mountains
   private def createMountains {
     for(s <- segments) {
-      println(s.mPoints.size)
+       if(s.mPoints.size > 0) {
-       if(s.mPoints.size > 2) {
          val mountain = new MonotoneMountain
-         // TODO: Optomize sort? The number of points should be 
+         val k = Util.msort((x: Point, y: Point) => x < y)(s.mPoints.toList)
-         // fairly small => insertion or merge?
+         val points = s.p :: k ::: List(s.q)
-         val points = s.mPoints.toList
+         points.foreach(p => mountain += p.clone)
-         for(p <- points.sort((e1,e2) => e1 < e2)) {
-           mountain += p.clone
-         }
          if(mountain.size > 2) {
            mountain.triangulate
            //mountain.monoPoly

src/org/poly2tri/Util.scala

@@ -3,6 +3,21 @@ package org.poly2tri
 
 import collection.jcl.ArrayList
 
+object Util {
+  
+  // From "Scala By Example," by Martin Odersky
+  def msort[A](less: (A, A) => Boolean)(xs: List[A]): List[A] = {
+    def merge(xs1: List[A], xs2: List[A]): List[A] =
+      if (xs1.isEmpty) xs2
+      else if (xs2.isEmpty) xs1
+      else if (less(xs1.head, xs2.head)) xs1.head :: merge(xs1.tail, xs2)
+      else xs2.head :: merge(xs1, xs2.tail)
+      val n = xs.length/2
+      if (n == 0) xs
+      else merge(msort(less)(xs take n), msort(less)(xs drop n))
+  }
+}
+
 /** The object <code>Random</code> offers a default implementation
  *  of scala.util.Random and random-related convenience methods.
  *
@@ -33,5 +48,5 @@ object Random extends scala.util.Random {
       swap(n - 1, k)
     }
     buf
-  }
+  } 
 }