# Find coordinates of intersection of vector and a square's edges

Not big problem, but I can't find a formula for the following stuff.

I have this kind of things:

(I was not able to draw vector in my application so I represented the source by point and the end of the arrow by nothing, and the vector is the segment) ; also don't pay attention the red ones on this image)

So I'll have a lot of vectors composed of a source point (inside the square) and a destination point (inside or outside the square).

The square is delimited by the four black points in the corners.

I need a formula to get the coordinates of the intersection with the edge (if there is one).

For example I'd need the coordinates of the "points" on the following image:

Anybody has an idea on how to achieve that?

• It is not clear how you define the red vectors and how they relate to the black vectors in the other drawing. You have 5 red vectors(?) in the square...
– Moti
Nov 19 '18 at 1:05
• Just edited my post. Nov 19 '18 at 7:46
• In your case, the direction seems to be irrelevant. Is there no reason you don't work with segments? (Also, note that vectors typically have magnitude and direction, but not a starting point - they can be "moved around" and still be the same vector). Nov 19 '18 at 8:34
• Yes I just don't know how to call a vector with a starting point, maybe a translation? I figured out a formula by myself anyways, I was a bit tired, that was not that hard finally sorry to annoye ans thanks. Nov 19 '18 at 9:47
• And yes direction was irrelevant you were right. Nov 19 '18 at 9:48