Question

I have two Line objects in C# WPF, and I’m trying to construct a method to work out the coordinates at which the lines intersect (if at all). After giving myself a headache reminding myself of high school maths to do this, I can’t work out how to map it into programming format – anyone know how to do this?

Thanks very much,
Becky

Answer 1

I suppose your line objects are made up of two points. What you should do is get the equations of both lines.

Then you should solve the following equation:

equation-line1 = equation-line2

Calculate slope of a line:

    float _slope = 1e+10;
    if ((p2.x - p1.x) != 0)
        _slope = (p2.y - p1.y) / (p2.x - p1.x);

p1 = Point 1 of your line
p2 = Point 2 of your line

Equation of a line:

y = ax + b

a = the slope you calculated
b = the intersect

Solving the equation:

    a1 = p1.y - b1 * p1.x;
    a2 = q1.y - b2 * q1.x;

    x = (a1 - a2) / (b2 - b1);
    y = a2 + b2 * x;

vars:

• b1 = slope line 1
• b2 = slop line 2
• q1 = point 1 of your 2nd line

So, x and y are the coordinates of the point where the two lines intersect