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vis_ninth.py
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vis_ninth.py
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import math
class VisibilityPolygon():
def compute(self, position, segments):
#print "compute"
polygon = []
sorted = self.sortPoints(position, segments);
map=[-1] * len(segments)
heap = []
start = [position[0] + 1, position[1]]
for i in xrange(len(segments)):
a1 = self.angle(segments[i][0], position)
a2 = self.angle(segments[i][1], position)
active = False
if (a1 > -180 and a1 <= 0 and a2 <= 180 and a2 >= 0 and a2 - a1 > 180):
active = True
if (a2 > -180 and a2 <= 0 and a1 <= 180 and a1 >= 0 and a1 - a2 > 180):
active = True
if active:
self.insert(i, heap, position, segments, start, map)
#print i, " active"
i=0
#print "len(sorted): ",len(sorted)
while i < (len(sorted)):
#print i
extend = False
shorten = False
orig = i
vertex = segments[sorted[i][0]][sorted[i][1]]
old_segment = heap[0]
while (sorted[i][2] < sorted[orig][2] + self.epsilon()):
if (map[sorted[i][0]] != -1):
if (sorted[i][0] == old_segment):
extend = True;
vertex = segments[sorted[i][0]][sorted[i][1]]
self.remove(map[sorted[i][0]], heap, position, segments, vertex, map);
else:
self.insert(sorted[i][0], heap, position, segments, vertex, map)
if (heap[0] != old_segment):
shorten = True
i+=1
#print i
if (i == len(sorted)):
break
if extend:
#print "extend"
polygon.append(vertex)
cur = self.intersectLines(segments[heap[0]][0], segments[heap[0]][1], position, vertex)
if not self.equal(cur, vertex):
polygon.append(cur)
#print "extend"
elif shorten:
#print "shorten"
polygon.append(self.intersectLines(segments[old_segment][0], segments[old_segment][1], position, vertex));
polygon.append(self.intersectLines(segments[heap[0]][0], segments[heap[0]][1], position, vertex));
#print "shorten"
return polygon
def sortPoints(self, position, segments):
#print "sortPoints"
points=[-1] * (len(segments)*2)
for i in xrange(len(segments)):
for j in range(2):
a=self.angle(segments[i][j], position)
points[2*i+j] = [i, j, a]
points.sort(key=lambda x: x[2]) # is this the same?? points.sort(function(a,b) {return a[2]-b[2];});
return points
def angle (self, a, b):
#print "angle"
return math.atan2(b[1]-a[1], b[0]-a[0]) * 180 / math.pi
def insert (self, index, heap, position, segments, destination, map):
print("insert")
intersect = self.intersectLines(segments[index][0], segments[index][1], position, destination)
if len(intersect) == 0:
return
cur = len(heap)
heap.append(index)
map[index] = cur
while (cur > 0):
parent = self.parent(cur)
if not self.lessThan(heap[cur], heap[parent], position, segments, destination):
break
map[heap[parent]] = cur
map[heap[cur]] = parent
temp = heap[cur]
heap[cur] = heap[parent]
heap[parent] = temp
cur = parent
def intersectLines(self, a1, a2, b1, b2):
#print "intersectLines:", a1, a2, b1, b2
a1 = map(float, a1)
a2 = map(float, a2)
b1 = map(float, b1)
b2 = map(float, b2)
ua_t = (b2[0] - b1[0]) * (a1[1] - b1[1]) - (b2[1] - b1[1]) * (a1[0] - b1[0])
ub_t = (a2[0] - a1[0]) * (a1[1] - b1[1]) - (a2[1] - a1[1]) * (a1[0] - b1[0])
u_b = (b2[1] - b1[1]) * (a2[0] - a1[0]) - (b2[0] - b1[0]) * (a2[1] - a1[1])
if (u_b != 0):
ua = ua_t / u_b
ub = ub_t / u_b
return [a1[0] - ua * (a1[0] - a2[0]), a1[1] - ua * (a1[1] - a2[1])]
return []
def parent (self, index):
#print "parent"
return int(math.floor((index-1)/2))
def lessThan (self, index1, index2, position, segments, destination):
#print "lessThan"
inter1 = self.intersectLines(segments[index1][0], segments[index1][1], position, destination)
inter2 = self.intersectLines(segments[index2][0], segments[index2][1], position, destination)
if not self.equal(inter1, inter2):
d1 = self.distance(inter1, position)
d2 = self.distance(inter2, position)
return d1 < d2
end1 = 0
if (self.equal(inter1, segments[index1][0])):
end1 = 1
end2 = 0
if (self.equal(inter2, segments[index2][0])):
end2 = 1
a1 = self.angle2(segments[index1][end1], inter1, position)
a2 = self.angle2(segments[index2][end2], inter2, position)
if (a1 < 180):
if (a2 > 180):
return True
return a2 < a1
return a1 < a2
def equal (self, a, b):
#print "equal"
if (abs(a[0] - b[0]) < self.epsilon() and abs(a[1] - b[1]) < self.epsilon()):
return True
return False
def epsilon (self):
return 0.0000001 #is this crazy, or what?
def distance (self, a, b):
return (a[0]-b[0])*(a[0]-b[0]) + (a[1]-b[1])*(a[1]-b[1])
def angle2(self, a, b, c):
a1 = self.angle(a,b)
a2 = self.angle(b,c)
a3 = a1 - a2;
if (a3 < 0):
a3 += 360
if (a3 > 360):
a3 -= 360
return a3
def remove (self, index, heap, position, segments, destination, map):
print("remove")
map[heap[index]] = -1
if (index == len(heap) - 1):
heap.pop()
return
heap[index] = heap.pop()
map[heap[index]] = index
cur = index
parent = self.parent(cur)
if (cur != 0 and self.lessThan(heap[cur], heap[parent], position, segments, destination)):
TMI=1000
while (cur > 0):
parent = self.parent(cur)
#print parent, cur
if not self.lessThan(heap[cur], heap[parent], position, segments, destination):
break
map[heap[parent]] = cur
map[heap[cur]] = parent
temp = heap[cur]
heap[cur] = heap[parent]
heap[parent] = temp
cur = parent
else:
while True:
left = self.child(cur);
right = left + 1;
if (left < len(heap) and self.lessThan(heap[left], heap[cur], position, segments, destination) and
(right == len(heap) or self.lessThan(heap[left], heap[right], position, segments, destination))):
map[heap[left]] = cur
map[heap[cur]] = left
temp = heap[left]
heap[left] = heap[cur]
heap[cur] = temp
cur = left
elif (right < len(heap) and self.lessThan(heap[right], heap[cur], position, segments, destination)):
map[heap[right]] = cur
map[heap[cur]] = right
temp = heap[right]
heap[right] = heap[cur]
heap[cur] = temp
cur = right
else:
break
def child (self,index):
return 2*index+1
def convertToSegments (self, polygons):
#print "convertToSegments"
segments = []
for i in xrange(len(polygons)):
for j in xrange(len(polygons[i])):
k = j+1
if (k == len(polygons[i])):
k = 0
segments.append([polygons[i][j], polygons[i][k]])
return segments
if __name__ == '__main__':
from PIL import Image, ImageDraw
VP=VisibilityPolygon()
polygons = []
#polygons.append([[-1,-1],[501,-1],[501,501],[-1,501]])
#polygons.append([[240,240],[260,240],[260,260],[240,260]])
#polygons.append([[240,260],[260,260],[260,280],[240,280]])
#polygons.append([[260,240],[280,240],[280,260],[260,260]])
#polygons.append([[440,240],[460,240],[460,260],[440,260]])
#polygons.append([[250,100],[260,140],[240,140]])
#polygons.append([[280,100],[290,60],[270,60]])
#polygons.append([[310,100],[320,140],[300,140]])
#polygons.append([[50,450],[60,370],[70,450]])
#polygons.append([[450,450],[460,370],[470,450]])
#polygons.append([[50,50],[60,30],[70,50]])
#polygons.append([[450,50],[460,30],[470,50]])
#polygons.append([[140,340],[160,240],[180,340],[360,340],[360,360],[250,390],[140,360]])
#polygons.append([[140,140],[150,130],[150,145],[165,150],[160,160],[140,160]])
polygons.append([[-24.0, -5.0], [-25.5, -5.0], [-25.5, -4.0], [-24.0, -4.0]])
polygons.append([[-24.0, 5.0], [-24.0, 4.0], [-25.5, 4.0], [-25.5, 5.0]])
polygons.append([[-34.0, 4.0], [-43.0, 4.0], [-42.5, -4.0], [-34.0, -4.0], [-32.0, -12.0], [-29.0, -14.0], [-24.0, -14.0], [-24.0, -23.5], [-16.0, -23.5], [-16.0, -4.0], [4.0, -4.0], [4.0, 4.0], [-16.0, 4.0], [-16.0, 14.0], [-26.0, 14.0], [-26.0, 34.0], [-44.0, 34.0], [-44.0, 26.5], [-34.0, 26.0]])
segments = VP.convertToSegments(polygons)
position = [3, 3]
visibility = VP.compute(position, segments)
print(visibility)
# Debug PIL Image out
image = Image.new("RGBA", (500,500), (0,0,0,1))
draw = ImageDraw.Draw(image)
for i in xrange(1, len(polygons)):
draw.polygon(map(tuple, polygons[i]), fill = 'red')
draw.polygon(map(tuple, visibility), fill = 'white')
draw.ellipse((position[0]-3, position[1]-3, position[0]+3, position[1]+3), fill='blue')
del draw
image.save("test.png", "PNG")