Can I find the intersection points of a line and a box?

I'm currently doing a university project which requires me to find the points of collision between a line and a box.

This is part of a motion prediction program. My inputs are two 2D co-ordinates of an object (two detected positions which occur one after the other) from which I plan to connect using a line. From this line, I will find the point of intersection with the box.

So far, I have written a some code that occasionally works. This is because I've been unable to represent the boundary as a box and I've just used the top and right edge of the table as limits.

My main question is, is it possible to represent the four sides of the box as a boundary and find out where the point of collision is according to the direction that the object is headed in?

Thanks

Sandy

Please note: I'm using the 2010 version of MATLAB

Here is a copy of my code

clc
clear

%Define Table
    x1=0;
    y1=0;
    x2=200;
    y2=100;

%Point 1
    A_x=50;
    A_y=30;

%Point 2
    B_x=60;
    B_y=60;

%Draw the points
    x_p=[A_x,B_x];
    y_p=[A_y,B_y];

%Equation of line between 2 points
    d=[B_x-A_x;B_y-A_y];

%Calculate time of collision at wall in x direction
    collisionx=(x2-B_x)/d(1,1);

%Calculate time of collision at wall in y direction
    collisiony=(y2-B_y)/d(2,1);

%Find point of collision
    if collisionx>collisiony
        p=[B_x;B_y]+collisiony*d
    else
        p=[B_x;B_y]+collisionx*d
    end

%Plot all points and table
    plot(x_p,y_p,'x',p(1),p(2),'o')
    axis([-20 220 -20 120])
    rectangle('Position',[x1,y1,x2,y2])

Answer 1

[Sean de Wolski]

I am sure a tool here FEX:query:polygon+intersect will likely help you a lot!

Answer 2

[Sandy]

Thank you very much for the hint - I found a function which did almost exactly what I need!

2D Polygon edges intersection:

http://www.mathworks.com/matlabcentral/fileexchange/27673-2d-polygon-edges-intersection