protected void setSlope(Point s, Point e) {
        slope = 0.0f;
        if ((double) last.x - (double) end.x != 0.0f) {
            slope = ((double) last.y - (double) end.y) / ((double) last.x - (double) end.x);
        } else if (last.y > end.y) {
            slope = 9999999.0f;
        } else if (last.y < end.y) {
            slope = -9999999.0f;
        }
    }