pvdz.ee - Intersection between two lines

Simple way of getting the point of intersection between two lines (A-AA and B-BB) on a (2d) plane.

Pass on the xy coordinates for all end points of the lines and you'll either get an object with x/y back or the falsy value null.

Not my math by the way. Got it from stackoverflow, where else.

Code:

function intersects(ax, ay, aax, aay, bx, by, bbx, bby){
  var sax = aax - ax;
  var say = aay - ay;
  var sbx = bbx - bx;
  var sby = bby - by;

  var s = (-say * (ax - bx) + sax * (ay - by)) / (-sbx * say + sax * sby);
  var t = ( sbx * (ay - by) - sby * (ax - bx)) / (-sbx * say + sax * sby);

  if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
    var x = ax + (t*sax);
    var y = ay + (t*say);

    return {x:x, y:y};
  }

  return null;
}

Interactive demo

Hope it helps ya :)