[HELP] Lines

[aqeelsfolio]

Line a: point(xa1,ya1) to point(xa2,ya2)
and
Line b: point(xb1,yb1) to point(xb2,yb2)

how can i know these two line intersect each other and at what point?

[jbum]

Here's a pretty good treatment of the problem.

http://astronomy.swin.edu.au/~pbourk...ry/lineline2d/

- Jim

[a_slosh]

if you want to first check they intercect then check that they aren't parallel:

gradient a:

(ya2-ya1)/(xa2-xa1)

gradient b:

(yb2-yb1)/(xb2-xb1)

these two values should be different

[aqeelsfolio]

i want to see if these two line intersect between their end points.

[a_slosh]

check the gradients then refer to jbum's link if they are not parallel or you can just get there equations and solve simultaneously if you're just doing it by hand

then check that the point of intersection (xi) is such that either xa1 < xi < xa2 or xa1 > xi > xa2 and so on for both x and y and both lines