判斷兩線段是否相交的C#代碼

今晚參考了 http://www.html-js.com/?p=1066&cpage=1 寫了判斷兩線段是否相交的c#代碼。基本思想是相交的兩條線段，對於任意一線段的兩端點，都在另一條直線的兩邊。

        /// <summary>
        /// 判斷直線2的兩點是否在直線1的兩邊。
        /// </summary>
        /// <param name="line1">直線1</param>
        /// <param name="line2">直線2</param>
        /// <returns></returns>
        private bool CheckCrose(Line line1, Line line2)
        {
            PointF v1 = new PointF();
            PointF v2 = new PointF();
            PointF v3 = new PointF();

            v1.X = line2.Start.X - line1.End.X;
            v1.Y = line2.Start.Y - line1.End.Y;

            v2.X = line2.End.X - line1.End.X;
            v2.Y = line2.End.Y - line1.End.Y;

            v3.X = line1.Start.X - line1.End.X;
            v3.Y = line1.Start.Y - line1.End.Y;

            return (CrossMul(v1, v3) * CrossMul(v2, v3) <= 0);

        }
        /// <summary>
        /// 判斷兩條線段是否相交。
        /// </summary>
        /// <param name="line1">線段1</param>
        /// <param name="line2">線段2</param>
        /// <returns>相交返回真，否則返回假。</returns>
        private bool CheckTwoLineCrose(Line line1, Line line2)
        {
            return CheckCrose(line1, line2) && CheckCrose(line2, line1);
        }
        /// <summary>
        /// 計算兩個向量的叉乘。
        /// </summary>
        /// <param name="pt1"></param>
        /// <param name="pt2"></param>
        /// <returns></returns>
        private float CrossMul(PointF pt1, PointF pt2)
        {
            return pt1.X * pt2.Y - pt1.Y * pt2.X;
        }