fixed seidel numerical accuracy bug

python/poly2tri.py

@@ -11,7 +11,7 @@ class Poly2Tri(Game):
         super(Poly2Tri, self).__init__(*self.screen_size)       
         
         # Load point set
-        file_name = "../data/dude.dat"
+        file_name = "../data/nazca_monkey.dat"
         self.points = self.load_points(file_name)
         
         # Triangulate
@@ -30,7 +30,7 @@ class Poly2Tri(Game):
         pass
         
     def render(self):
-        reset_zoom(2.0, (400, 500), self.screen_size)
+        reset_zoom(8, (0, 0), self.screen_size)
         red = 255, 0, 0
         for t in self.triangles:
             draw_polygon(t, red)

python/seidel.py

@@ -30,7 +30,7 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 # 
 from random import shuffle
-from math import atan2, floor
+from math import atan2
 
 ##
 ## Based on Raimund Seidel'e paper "A simple and fast incremental randomized
@@ -94,10 +94,12 @@ class Edge(object):
         self.mpoints.append(q)
           
     def is_above(self, point):
-        return (floor(point.y) < floor(self.slope * point.x + self.b))
+        # NOTE rounding can effect numerical robustness
+        return (round(point.y, 10) < round(self.slope * point.x + self.b, 10))
         
     def is_below(self, point):
-        return (floor(point.y) > floor(self.slope * point.x + self.b))
+        # NOTE rounding can effect numerical robustness
+        return (round(point.y, 10) > round(self.slope * point.x + self.b, 10))
 
     def intersect(self, c, d):
         a = self.p