def __init__(self, segment_list):
self.event_queue = PriorityQueue() # sorted along x
self.sweep_line = SlowTree() # sorted along y
for segment in segment_list:
# Zalozone segment.pt1.x < segment.pt2.x.
# Trzeba obsluzyc druga mozliwosc.
if segment.pt1.x > segment.pt2.x:
segment = ~segment
self.event_queue.push(Event(segment.pt1, Event.LEFT, segment))
self.event_queue.push(Event(segment.pt2, Event.RIGHT, segment))
def test_pq(self):
pq = PriorityQueue()
self.assertTrue(pq.empty())
self.assertEqual(len(pq), 0)
self.assertEqual(str(pq), "[]")
pq.push(3)
self.assertFalse(pq.empty())
self.assertEqual(len(pq), 1)
self.assertEqual(str(pq), "[3]")
pq.push(3) # ignored
self.assertEqual(len(pq), 1)
pq.push(5)
self.assertEqual(len(pq), 2)
pq.push(2)
self.assertEqual(str(pq), "[2, 5, 3]") # heap
self.assertEqual(len(pq), 3)
self.assertEqual(pq.pop(), 2)
self.assertEqual(pq.pop(), 3)
self.assertEqual(pq.pop(), 5)
class ShamosHoey:
"""Shamos-Hoey algorithm - educational version.
http://geomalgorithms.com/a09-_intersect-3.html
"""
def __init__(self, segment_list):
self.event_queue = PriorityQueue() # sorted along x
self.sweep_line = SlowTree() # sorted along y
for segment in segment_list:
# Zalozone segment.pt1.x < segment.pt2.x.
# Trzeba obsluzyc druga mozliwosc.
if segment.pt1.x > segment.pt2.x:
segment = ~segment
self.event_queue.push(Event(segment.pt1, Event.LEFT, segment))
self.event_queue.push(Event(segment.pt2, Event.RIGHT, segment))
def run(self):
while not self.event_queue.empty():
event = self.event_queue.pop()
if event.type == Event.LEFT:
if self._handle_left_endpoint(event):
return True
elif event.type == Event.RIGHT:
if self._handle_right_endpoint(event):
return True
else:
raise ValueError("unknown event")
return False
def _handle_left_endpoint(self, event):
segment_e = event.segment # Let segE = E's segment
self.sweep_line.insert(segment_e) # Add segE to SL
segment_above = self.sweep_line.successor(segment_e) # Let segA = the segment Above segE in SL
segment_below = self.sweep_line.predecessor(segment_e) # Let segB = the segment Below segE in SL
if segment_above: # if exists
segment_above = segment_above.value # get segment from node
if segment_e.intersect(segment_above): # If (I = Intersect( segE with segA) exists)
return True
if segment_below: # if exists
segment_below = segment_below.value # get segment from node
if segment_e.intersect(segment_below): # If (I = Intersect( segE with segB) exists)
return True
return False
def _handle_right_endpoint(self, event):
segment_e = event.segment # Let segE = E's segment
segment_above = self.sweep_line.successor(segment_e) # Let segA = the segment Above segE in SL
segment_below = self.sweep_line.predecessor(segment_e) # Let segB = the segment Below segE in SL
if segment_above and segment_below: # if exists
segment_above = segment_above.value # get segment from node
segment_below = segment_below.value # get segment from node
if segment_above.intersect(segment_below): # If (I = Intersect( segA with segB) exists)
return True
self.sweep_line.remove(segment_e)
return False
class BentleyOttmann:
"""Bentley-Ottmann algorithm - educational version."""
def __init__(self, segment_list):
self.event_queue = PriorityQueue() # sorted along x
self.sweep_line = SlowTree() # sorted along y
for segment in segment_list:
# Zalozone segment.pt1.x < segment.pt2.x.
# Trzeba obsluzyc druga mozliwosc.
if segment.pt1.x > segment.pt2.x:
segment = ~segment
self.event_queue.push(Event(segment.pt1, Event.LEFT, segment))
self.event_queue.push(Event(segment.pt2, Event.RIGHT, segment))
self.il = [] # intersection list
def run(self):
while not self.event_queue.empty():
event = self.event_queue.pop()
if event.type == Event.LEFT:
self._handle_left_endpoint(event)
elif event.type == Event.RIGHT:
self._handle_right_endpoint(event)
elif event.type == Event.CROSSING:
self._handle_crossing(event)
else:
raise ValueError("unknown event")
del self.event_queue
del self.sweep_line
return self.il
def _handle_left_endpoint(self, event):
segment_e = event.segment # Let segE = E's segment
self.sweep_line.insert(segment_e) # Add segE to SL
segment_above = self.sweep_line.successor(
segment_e) # Let segA = the segment Above segE in SL
segment_below = self.sweep_line.predecessor(
segment_e) # Let segB = the segment Below segE in SL
if segment_above: # if exists
segment_above = segment_above.value # get segment from node
point = segment_e.intersection_point(segment_above)
if point and point.x > event.point.x:
self.event_queue.push(
Event(point, Event.CROSSING, segment_above, segment_e))
if segment_below: # if exists
segment_below = segment_below.value # get segment from node
point = segment_e.intersection_point(segment_below)
if point and point.x > event.point.x:
self.event_queue.push(
Event(point, Event.CROSSING, segment_e, segment_below))
def _handle_right_endpoint(self, event):
segment_e = event.segment # Let segE = E's segment
segment_above = self.sweep_line.successor(
segment_e) # Let segA = the segment Above segE in SL
segment_below = self.sweep_line.predecessor(
segment_e) # Let segB = the segment Below segE in SL
if segment_above and segment_below: # if exists
segment_above = segment_above.value # get segment from node
segment_below = segment_below.value # get segment from node
point = segment_above.intersection_point(segment_below)
if point and point.x > event.point.x:
self.event_queue.push(
Event(point, Event.CROSSING, segment_above, segment_below))
self.sweep_line.remove(segment_e)
def _handle_crossing(self, event):
self.il.append(
event.point) # Add Es intersect point to the output list IL
# Let segE1 above segE2 be E's intersecting segments in SL
segment_e1 = event.segment_above
segment_e2 = event.segment_below
# Swap their positions so that segE2 is now above segE1;
self.sweep_line.swap(segment_e1, segment_e2)
segment_above_e2 = self.sweep_line.successor(
segment_e2) # Let segA = the segment above segE2 in SL
segment_below_e1 = self.sweep_line.predecessor(
segment_e1) # Let segB = the segment below segE1 in SL
if segment_above_e2:
segment_above_e2 = segment_above_e2.value
point = segment_above_e2.intersection_point(segment_e2)
if point and point.x > event.point.x:
self.event_queue.push(
Event(point, Event.CROSSING, segment_above_e2, segment_e2))
if segment_below_e1:
segment_below_e1 = segment_below_e1.value
point = segment_below_e1.intersection_point(segment_e1)
if point and point.x > event.point.x:
self.event_queue.push(
Event(point, Event.CROSSING, segment_e1, segment_below_e1))