Raphael.fn.drawGrid = function (x, y, w, h, wv, hv, color) {
    color = color || "#000";
    var path = ["M", Math.round(x) + .5, Math.round(y) + .5, "L", Math.round(x + w) + .5, Math.round(y) + .5, Math.round(x + w) + .5, Math.round(y + h) + .5, Math.round(x) + .5, Math.round(y + h) + .5, Math.round(x) + .5, Math.round(y) + .5],
        rowHeight = h / hv,
        columnWidth = w / wv;
    for (var i = 1; i < hv; i++) {
        path = path.concat(["M", Math.round(x) + .5, Math.round(y + i * rowHeight) + .5, "H", Math.round(x + w) + .5]);
    }
    for (i = 1; i < wv; i++) {
        path = path.concat(["M", Math.round(x + i * columnWidth) + .5, Math.round(y) + .5, "V", Math.round(y + h) + .5]);
    }
    return this.path(path.join(",")).attr({stroke: color});
};

function getAnchors(p1x, p1y, p2x, p2y, p3x, p3y) {
        var l1 = (p2x - p1x) / 2,
            l2 = (p3x - p2x) / 2,
            a = Math.atan((p2x - p1x) / Math.abs(p2y - p1y)),
            b = Math.atan((p3x - p2x) / Math.abs(p2y - p3y));
        a = p1y < p2y ? Math.PI - a : a;
        b = p3y < p2y ? Math.PI - b : b;
        var alpha = Math.PI / 2 - ((a + b) % (Math.PI * 2)) / 2,
            dx1 = l1 * Math.sin(alpha + a),
            dy1 = l1 * Math.cos(alpha + a),
            dx2 = l2 * Math.sin(alpha + b),
            dy2 = l2 * Math.cos(alpha + b);
        return {
            x1: p2x - dx1,
            y1: p2y + dy1,
            x2: p2x + dx2,
            y2: p2y + dy2
        };
}