def insert_arc_among_existing(self, point):
arc = self.beach_line
while arc is not None:
intersection_point = check_if_arc_intersects(point, arc)
if intersection_point is not None:
second_intersection_point = check_if_arc_intersects(
point, arc.next)
if arc.next is not None and second_intersection_point is None:
arc.next.prev = Arc(arc.point, arc, arc.next)
arc.next = arc.next.prev
else:
arc.next = Arc(arc.point, arc)
arc.next.lower_edge = arc.lower_edge
arc.next.prev = Arc(point, arc, arc.next)
arc.next = arc.next.prev
arc = arc.next
edge = Edge(intersection_point)
self.voronoi.append(edge)
arc.prev.lower_edge = arc.upper_edge = edge
edge = Edge(intersection_point)
self.voronoi.append(edge)
arc.next.upper_edge = arc.lower_edge = edge
self.check_circle_event(arc)
self.check_circle_event(arc.prev)
self.check_circle_event(arc.next)
return True
arc = arc.next
return False
def arc_insert(self, p):
if self.arc is None:
self.arc = Arc(p)
else:
# find the current arcs at p.y
i = self.arc
while i is not None:
flag, z = self.intersect(p, i)
if flag:
# new parabola intersects arc i
flag, zz = self.intersect(p, i.pnext)
if (i.pnext is not None) and (not flag):
i.pnext.pprev = Arc(i.p, i, i.pnext)
i.pnext = i.pnext.pprev
else:
i.pnext = Arc(i.p, i)
i.pnext.s1 = i.s1
# add p between i and i.pnext
i.pnext.pprev = Arc(p, i, i.pnext)
i.pnext = i.pnext.pprev
i = i.pnext # now i points to the new arc
# add new half-edges connected to i's endpoints
seg = Segment(z)
self.output.append(seg)
i.pprev.s1 = i.s0 = seg
seg = Segment(z)
self.output.append(seg)
i.pnext.s0 = i.s1 = seg
# check for new circle events around the new arc
self.check_circle_event(i, p.x)
self.check_circle_event(i.pprev, p.x)
self.check_circle_event(i.pnext, p.x)
return
i = i.pnext
# if p never intersects an arc, append it to the list
i = self.arc
while i.pnext is not None:
i = i.pnext
i.pnext = Arc(p, i)
# insert new segment between p and i
x = self.x0
y = (i.pnext.p.y + i.p.y) / 2.0;
start = Point(x, y)
seg = Segment(start)
i.s1 = i.pnext.s0 = seg
self.output.append(seg)
def insert_arc(self, point):
if self.beach_line is None:
self.beach_line = Arc(point)
return
if self.insert_arc_among_existing(point):
return
arc = self.beach_line
while arc.next is not None:
arc = arc.next
arc.next = Arc(point, arc)
x = self.LEFT
y = (arc.next.point.y + arc.point.y) / 2.0
start = Point(x, y)
edge = Edge(start)
arc.lower_edge = arc.next.upper_edge = edge
self.voronoi.append(edge)