intersect.js

gistfile1.txt

Intersection.intersectLineLine = function(a1, a2, b1, b2) {
    var result;
    
    var ua_t = (b2.x - b1.x) * (a1.y - b1.y) - (b2.y - b1.y) * (a1.x - b1.x);
    var ub_t = (a2.x - a1.x) * (a1.y - b1.y) - (a2.y - a1.y) * (a1.x - b1.x);
    var u_b  = (b2.y - b1.y) * (a2.x - a1.x) - (b2.x - b1.x) * (a2.y - a1.y);

    if ( u_b != 0 ) {
        var ua = ua_t / u_b;
        var ub = ub_t / u_b;

        if ( 0 <= ua && ua <= 1 && 0 <= ub && ub <= 1 ) {
            result = new Intersection("Intersection");
            result.points.push(
                new Point2D(
                    a1.x + ua * (a2.x - a1.x),
                    a1.y + ua * (a2.y - a1.y)
                )
            );
        } else {
            result = new Intersection("No Intersection");
        }
    } else {
        if ( ua_t == 0 || ub_t == 0 ) {
            result = new Intersection("Coincident");
        } else {
            result = new Intersection("Parallel");
        }
    }

    return result;
};