Skip to content

Instantly share code, notes, and snippets.

@isedgar

isedgar/ray_casting.py

Created June 20, 2023 13:45
Show Gist options
  • Save isedgar/9bf444faa5b1bb3c298e42311bf2cf39 to your computer and use it in GitHub Desktop.
Save isedgar/9bf444faa5b1bb3c298e42311bf2cf39 to your computer and use it in GitHub Desktop.
Download ZIP
Raw
ray_casting.py
def ray_casting(point, polygon):
intersections = 0
x, y = point
for k in range(len(polygon)-1):
x1, y1 = polygon[k]
x2, y2 = polygon[k+1]
if (y < y1) != (y < y2) and\
x < (x2-x1)*(y-y1)/(y2-y1)+x1:
intersections += 1
return intersections % 2 == 1
def point_on_side(point, polygon): # when the point lies on a side of the polygon
is_on_a_side = False
x, y = point
for k in range(len(polygon)-1):
x1, y1 = polygon[k]
x2, y2 = polygon[k+1]
if (y < y1) != (y < y2) and\
(x < x1) != (x < x2) and\
(x2-x1)*(y-y1)==(x-x1)*(y2-y1):
is_on_a_side = True
break
return is_on_a_side
from random import uniform
from numpy import array
from matplotlib import pyplot as plt
X = []
Y = []
P = [
[1.31,3.53], [0.32,1.49],
[0.32,0.18], [3.22,0.18],
[4.12,2.03], [1.2,1.72],
[2.19,3.76], [1.5,4.32],
[0.35,3.53], [1.31,3.53]
]
colors = []
for i in range(2000):
x = uniform(-1, 5)
y = uniform(-1, 5)
X.append(x)
Y.append(y)
if ray_casting([x,y], P):
colors.append('green')
else:
colors.append('red')
x1 = P[5][0]
y1 = P[5][1]
x2 = P[6][0]
y2 = P[6][1]
x = (x1+x2)/2
y = ((y2-y1)/(x2-x1))*(x-x1) + y1
_point_on_side = [x,y]
plt.plot(array(P)[:,0], array(P)[:,1], color='gray', linewidth = 1)
plt.scatter(X, Y, c=colors, s=2)
plt.scatter([x], [y], c='blue', s=8)
plt.show()
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment