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))
def setUp(self):
segment1 = Segment(0, 0, 4, 4)
segment2 = Segment(1, 3, 3, 1)
self.event1 = Event(segment1.pt1, Event.LEFT, segment1)
self.event2 = Event(segment1.pt2, Event.RIGHT, segment1)
self.event3 = Event(Point(2, 2), Event.CROSSING, segment2, segment1)
segment3 = Segment(0, 0, 0, 1)
segment4 = Segment(0, 0, 1, 0)
self.event4 = Event(segment3.pt1, Event.VERTICAL, segment3)
self.event5 = Event(segment4.pt1, Event.HORIZONTAL, segment4)
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 __init__(self, segment_list):
"""Initialize structures."""
self.event_queue = [] # sorted along y
self.sweep_line = AVLTree() # sorted along x
for segment in segment_list: # O(n) time
if segment.pt1 > segment.pt2:
# (x1 > x2 and y1 = y2) or (x1 = x2 and y1 > y2)
segment = ~segment
if segment.pt1.x == segment.pt2.x: # vertical segment
self.event_queue.append(Event(segment.pt1, Event.BOTTOM, segment))
self.event_queue.append(Event(segment.pt2, Event.TOP, segment))
elif segment.pt1.y == segment.pt2.y: # horizontal segment
self.event_queue.append(Event(segment.pt1, Event.HORIZONTAL, segment))
else:
raise ValueError("horizontal or vertical segments are allowed")
self.event_queue.sort(key=lambda event: event.point.y) # O(n log n) time
self.il = [] # intersection list
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))