Create new data from the overlap of two polygons/polylines

Question

If we have two vector data such as polygons or polylines (shown in graph below). How can we get find the overlap and create a new x,y vector data for this new shape? (or simply get the area of the new shape.

import numpy as np
import matplotlib.pyplot as plt

x1 = [10, 20, 40, 50, 50, 40, 20, 10, 10];
y1 = [20, 10, 10, 20, 40, 50, 50, 40, 20];

x2 = [30, 60, 30, 0, 30];
y2 = [40, 50, 70, 60, 40];

fig, ax = plt.subplots()
ax.plot(x1, y1)
ax.plot(x2, y2)
plt.show()

For example, for the above graph where the intersections are, can we get the x,y coordinates/data for this new shape created from the overlap? or get the area of it instead?

We can. Compute line intersections and "paste" the lines together. — Ander Biguri, Sep 25 '20 at 11:40
@AnderBiguri: I mean, how does this help the OP ? Anyone can see it. — , Sep 25 '20 at 12:54
@YvesDaoust anyone can go and google how to do those steps too! Yet here we are. I explained the steps, so OP can go and research how to do those individually by themselves. Because that is what I (and others in SO) expect from OPs. — Ander Biguri, Sep 25 '20 at 13:22
@AnderBiguri: you explained nothing, just threw a few words, which a not even relevant keywords. — , Sep 25 '20 at 13:30
@Yves the ones you used in your almost link only answer.... Yeah. — Ander Biguri, Sep 25 '20 at 16:49

score 2 · Answer 1 · answered Sep 25 '20 at 12:23

2

Constructing the intersection of two polygons is uneasy in the general case. https://en.wikipedia.org/wiki/Vatti_clipping_algorithm

When the polygons are convex, as in your example, you can use the Sutherland-Hodgman algorithm. https://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm

answered Sep 25 '20 at 12:23

that seems interesting, i never seen this method before. i'll try put it in code update later – SGhaleb Sep 25 '20 at 12:43

Create new data from the overlap of two polygons/polylines

1 Answers1