Optimize the contour creation.

Region.cs

@@ -151,38 +151,33 @@ namespace Boprs
 			// Lexico-graphically sort the vertices.
 			vertices.Sort();
 
-			// Sweepline to keep track of edges.
-			SweepLine sweepLine = new SweepLine();
-
 			bool[] processed = new bool[vertices.Count]; 
 			List<Contour> contours = new List<Contour>();
 
 			for(int i = 0; i < vertices.Count; i++)
 			{
-				SweepVertex acVx = vertices[i];
+				// If we already traversed this vertex, skip it.
-
-				if (acVx.IsLeft())
-				{
-					sweepLine.Add(acVx.Edge, false);
-				}
-				else
-				{ 
-					sweepLine.Remove(acVx.Edge);
-				}
-
 				if (processed[i])
 				{
 					continue;
 				}
 
+				// Otherwise this is an edge on an indiscovered contour, create it.
 				Contour contour = new Contour();
 				contours.Add(contour);
 
-				SweepEdge prev = sweepLine.PrevEdge(acVx.Edge);
+				// acVx should be guaranteed to be the lowest and leftest vertex of the new polygon.
-				bool shouldBeCW = prev == null ? false : prev.TransitionInside;
+				// Thus it cannot be vertical.
+				// if it is transition inside, it is a positive contour and should wind counter-clockwise,
+				// if it is transition outside, it is a negative contour and should wind clockwise.
+				SweepVertex acVx = vertices[i];
+				bool shouldBeCW = !acVx.Edge.TransitionInside;
 
 				Point2d target = acVx.Point;
 
+
+				// Traverse connected edges, and mark taversed vertices as processed,
+				// until we loop back to the first discovered vertex on the contour.
 				int pos = i;
 				processed[i] = true;
 				contour.Vertices.Add(vertices[pos].Point);
@@ -200,6 +195,7 @@ namespace Boprs
 				}
 				processed[vertices.IndexOf(vertices[pos].OtherVertex())] = true;
 				
+				// If the contour is a hole and winds ccw, or positive and winds cw, flip it.
 				if (shouldBeCW != contour.IsClockwise())
 				{
 					contour.Reverse();