Function segmentsIntersect

src/lib/geometry2d.js:10–27

(x1, y1, x2, y2, x3, y3, x4, y4)

 */
exports.segmentsIntersect = segmentsIntersect;
function segmentsIntersect(x1, y1, x2, y2, x3, y3, x4, y4) {
    var a = x2 - x1;
    var b = x3 - x1;
    var c = x4 - x3;
    var d = y2 - y1;
    var e = y3 - y1;
    var f = y4 - y3;
    var det = a * f - c * d;
    // parallel lines? intersection is undefined
    // ignore the case where they are colinear
    if(det === 0) return null;
    var t = (b * f - c * e) / det;
    var u = (b * d - a * e) / det;
    // segments do not intersect?
    if(u < 0 || u > 1 || t < 0 || t > 1) return null;

    return {x: x1 + a * t, y: y1 + d * t};
}

/*
 * find the minimum distance between two line segments (1->2 and 3->4)