How would I use numpy to calculate the intersection between two line segments?
In the code I have segment1 = ((x1,y1),(x2,y2)) and segment2 = ((x1,y1),(x2,y2)). Note segment 1 does not equal segment2. So in my code I've also been calculating the slope and y-intercept, it would be nice if that could be avoided but I don't know of a way how.
I've been using Cramer's rule with a function I wrote up in Python but I'd like to find a faster way of doing this.
Stolen directly from http://www.cs.mun.ca/~rod/2500/notes/numpy-arrays/numpy-arrays.html
# # line segment intersection using vectors # see Computer Graphics by F.S. Hill # from numpy import * def perp( a ) : b = empty_like(a) b = -a b = a return b # line segment a given by endpoints a1, a2 # line segment b given by endpoints b1, b2 # return def seg_intersect(a1,a2, b1,b2) : da = a2-a1 db = b2-b1 dp = a1-b1 dap = perp(da) denom = dot( dap, db) num = dot( dap, dp ) return (num / denom.astype(float))*db + b1 p1 = array( [0.0, 0.0] ) p2 = array( [1.0, 0.0] ) p3 = array( [4.0, -5.0] ) p4 = array( [4.0, 2.0] ) print seg_intersect( p1,p2, p3,p4) p1 = array( [2.0, 2.0] ) p2 = array( [4.0, 3.0] ) p3 = array( [6.0, 0.0] ) p4 = array( [6.0, 3.0] ) print seg_intersect( p1,p2, p3,p4)