fixed legalization bug

src/org/poly2tri/cdt/CDT.scala

@@ -126,7 +126,7 @@ class CDT(val points: List[Point], val segments: List[Segment], iTriangle: Trian
   // Implement sweep-line 
   private def sweep {
     //var cTri: Triangle = null
-    for(i <- 1 until 15 /*points.size*/) {
+    for(i <- 1 until points.size) {
       val point = points(i)
       // Process Point event
       var triangle: Triangle = null
@@ -149,9 +149,6 @@ class CDT(val points: List[Point], val segments: List[Segment], iTriangle: Trian
     
     val node = aFront.locate(point)
 
-    // Avoid triangles that are almost collinear
-    if(!Util.collinear(point, node.point, node.next.point)) {
-    
     // Projected point coincides with existing point; create two triangles
     if(point.x == node.point.x && node.prev != null) {
         
@@ -217,11 +214,6 @@ class CDT(val points: List[Point], val segments: List[Segment], iTriangle: Trian
 	    scanAFront(newNode)
 	    newNode.triangle
 	}
-    
-    } else {
-      println("bad triangle")
-      null
-    }
   }
   
   // EdgeEvent
@@ -412,9 +404,10 @@ class CDT(val points: List[Point], val segments: List[Segment], iTriangle: Trian
       
       val sinA = v1 cross v2
       val sinB = v3 cross v4
-      //println((cosA*sinB + sinA*cosB))
-      // Some small number
-      if((cosA*sinB + sinA*cosB) < -10f) 
+
+      // Small negative number to prevent swapping
+      // in nearly neutral cases
+      if((cosA*sinB + sinA*cosB) < -0.01f) 
         true
       else
         false
@@ -426,7 +419,15 @@ class CDT(val points: List[Point], val segments: List[Segment], iTriangle: Trian
     
     val oPoint = t2 oppositePoint t1
     
-    if(illegal(t1.points(1), oPoint, t1.points(2), t1.points(0))) {
+    // Prevent creation of collinear traingles
+    val c1 = Util.collinear(t1.points(0), t1.points(1), oPoint)
+    val c2 = Util.collinear(t2.points(0), t2.points(1), oPoint)
+    val c3 = Util.collinear(t2.points(1), t2.points(2), oPoint)
+    val c4 = Util.collinear(t2.points(0), t2.points(2), oPoint)
+    val collinear = !(c1 && c2 && c3 && c4)
+    
+    if(illegal(t1.points(1), oPoint, t1.points(2), t1.points(0)) && !collinear) {
+
        println("legalize")
         // Update neighbor pointers
         val ccwNeighbor = t2.neighborCCW(oPoint)

src/org/poly2tri/shapes/Triangle.scala

@@ -45,7 +45,7 @@ class Triangle(val points: Array[Point], val neighbors: Array[Triangle]) {
   var clean = false
   
   // Update neighbor pointers
-  def updateNeighbors(ccwPoint: Point, cwPoint: Point, triangle: Triangle, mesh: HashSet[Triangle]) {
+  def updateNeighbors(ccwPoint: Point, cwPoint: Point, triangle: Triangle, debug: HashSet[Triangle]) {
     if((ccwPoint == points(2) && cwPoint == points(1)) || (ccwPoint == points(1) && cwPoint == points(2))) 
       neighbors(0) = triangle 
     else if((ccwPoint == points(0) && cwPoint == points(2)) || (ccwPoint == points(2) && cwPoint == points(0)))
@@ -53,9 +53,7 @@ class Triangle(val points: Array[Point], val neighbors: Array[Triangle]) {
     else if((ccwPoint == points(0) && cwPoint == points(1)) || (ccwPoint == points(1) && cwPoint == points(0)))
       neighbors(2) = triangle
     else {
-      mesh += triangle
-      println(ccwPoint + "," + cwPoint)
-      printDebug
+      debug += triangle
       throw new Exception("Neighbor update error")
     }
   }

src/org/poly2tri/utils/Util.scala

@@ -7,7 +7,8 @@ import shapes.Point
 
 object Util {
   
-  val COLLINEAR_SLOP = 10f
+  // Almost zero
+  val COLLINEAR_SLOP = 0.1f
   
   // From "Scala By Example," by Martin Odersky
   def msort[A](less: (A, A) => Boolean)(xs: List[A]): List[A] = {
@@ -39,23 +40,18 @@ object Util {
   // Tests if the given points are collinear
   def collinear(p1: Point, p2: Point, p3: Point): Boolean = {
     
-    // 3x3 matrix
+    // 3x2 matrix
     val a11 = p1.x
     val a12 = p1.y
-    val a13 = 1f
     val a21 = p2.x
     val a22 = p2.y
-    val a23 = 1f
     val a31 = p3.x
     val a32 = p3.y
-    val a33 = 1f
     
     // Determinant
-    val d = a11*(a22*a33 - a32*a23) - a12*(a21*a33-a31*a23) + a13*(a21*a32-a31*a22)
+    val d = a11*(a22-a32) - a12*(a21-a31) + (a21*a32-a31*a22)
 
-    println("Determinant = " + d)
-    
-    if(d <= COLLINEAR_SLOP) {
+    if(Math.abs(d) <= COLLINEAR_SLOP) {
       true
     } else {
       false