确定线段是否与多边形相交 [英] Determine if a line segment intersects a polygon
问题描述
如果我在2D平面上有一个矢量(由2个点组成的线),如何确定它是否已通过多边形?
If I have a vector (a line consisting of 2 points) on a 2D plane how can I determine if it has passed through a polygon?
我知道我可以乘以组成多边形的每条线,看看是否有相交,但是有更好的方法吗?
I know I can take each line which makes up the polygon and see if any intersect but is there a better way?
我已经阅读了这篇文章如何确定2D点是否在其中一个多边形?这给了我一些想法,以了解该点是否在多边形内,但是我需要查看它是否已通过/相交.
I've read this one post How can I determine whether a 2D Point is within a Polygon? which gives me some ideas for seeing whether the point is within a polygon but I need to see if it has passed over/intersected it.
推荐答案
如果您要使用Python库进行几何运算,请查看 shapely
.它使它像someline.intersects(somepolygon)
一样简单.
If you want a python library for geometric operations, have a look at shapely
. It makes this as simple as someline.intersects(somepolygon)
.
这是一个相交,缓冲区和剪切的快速示例(有一个漂亮的图...我正在使用
Here's a quick example of intersections, buffer, and clipping (with a nice plot... I'm using descartes
to easily convert shapely polygons into matplotlib patches.).
import numpy as np
import matplotlib.pyplot as plt
import shapely.geometry
import descartes
circle = shapely.geometry.Point(5.0, 0.0).buffer(10.0)
clip_poly = shapely.geometry.Polygon([[-9.5, -2], [2, 2], [3, 4], [-1, 3]])
clipped_shape = circle.difference(clip_poly)
line = shapely.geometry.LineString([[-10, -5], [15, 5]])
line2 = shapely.geometry.LineString([[-10, -5], [-5, 0], [2, 3]])
print 'Blue line intersects clipped shape:', line.intersects(clipped_shape)
print 'Green line intersects clipped shape:', line2.intersects(clipped_shape)
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(*np.array(line).T, color='blue', linewidth=3, solid_capstyle='round')
ax.plot(*np.array(line2).T, color='green', linewidth=3, solid_capstyle='round')
ax.add_patch(descartes.PolygonPatch(clipped_shape, fc='blue', alpha=0.5))
ax.axis('equal')
plt.show()
这将产生:
Blue line intersects clipped shape: True
Green line intersects clipped shape: False
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