判斷兩條線段是否相交__c

判斷兩條線段是否相交，可以採用向量積的方式來判斷，如下圖所示：

 

 

現定義一個函數初步判斷兩線段是否相交，如下代碼：

        /// <summary>

        /// 初步根據外圍框大致判斷兩條線段是否相交

        /// </summary>

        /// <param name="line01Coords">線段1的座標，長度為6</param>

        /// <param name="line02Coords">線段2的座標，長度為6</param>

        /// <returns>傳回型別為bool，如果為true表示兩條線段可能相交，如果為false表示兩條線段不相交</returns>

        private bool JudgeAboutCrossStatus(double[] line01Coords, double[] line02Coords)

        {

            bool returnResult = true;

            //先判斷在XY方向的最值

            double maxX1, minX1, maxY1, minY1;

            maxX1 = minX1 = line01Coords[0];

            maxY1 = minY1 = line01Coords[1];

            if (line01Coords[0] < line01Coords[3])

                maxX1 = line01Coords[3];

            else

                minX1 = line01Coords[3];

            if (line01Coords[1] < line01Coords[4])

                maxY1 = line01Coords[4];

            else

                minY1 = line01Coords[4];

            double maxX2, minX2, maxY2, minY2;

            maxX2 = minX2 = line02Coords[0];

            maxY2 = minY2 = line02Coords[1];

            if (line02Coords[0] < line02Coords[3])

                maxX2 = line02Coords[3];

            else

                minX2 = line02Coords[3];

            if (line02Coords[1] < line02Coords[4])

                maxY2 = line02Coords[4];

            else

                minY2 = line02Coords[4];

            //比較最值大小

            if ((minX1 > maxX2) || (maxX1 < minX2) || (minY1 > maxY2) || (maxY1 < minY2))

            {

                returnResult = false;

            }

            return returnResult;

        }

函數JudgeAboutCrossStatus()如果傳回值為true則表示兩條線段可能相交，則需要採用向量積的方式來判斷是否相交，如果為false則表示兩條線段不相交。現在定義一個函數Judge2LinesRelation ()用於判斷兩條線段是否相交，其代碼如下：

        /// <summary>

        /// 判斷兩條線段是否相交

        /// </summary>

        /// <param name="line01Coords">線段1的座標，長度為6</param>

        /// <param name="line02Coords">線段2的座標，長度為6</param>

        /// <returns>傳回型別為bool，如果為true表示兩條線段相交，如果為false表示兩條線段不相交</returns>

        private bool Judge2LinesRelation(double[] line01Coords, double[] line02Coords)

        {

            bool returnResult = true;

            returnResult = JudgeAboutCrossStatus(line01Coords, line02Coords);

            if (returnResult)//初步判斷兩條線段可能相交

            {

                double BAx, BAy, BCx, BCy, BDx, BDy, BABCk, BABDk;

                BAx = line01Coords[0] - line01Coords[3];

                BAy = line01Coords[1] - line01Coords[4];

                BCx = line02Coords[0] - line01Coords[3];

                BCy = line02Coords[1] - line01Coords[4];

                BABCk = BAx * BCy - BAy * BCx;

                BDx = line02Coords[3] - line01Coords[3];

                BDy = line02Coords[4] - line01Coords[4];

                BABDk = BAx * BDy - BAy * BDx;

                if (((BABCk > 0) && (BABDk > 0)) || ((BABCk < 0) && (BABDk < 0)))

                {

                    returnResult = false;

                }

                else if (((BABCk > 0) && (BABDk < 0)) || ((BABCk < 0) && (BABDk > 0)))

                {

                    double BCBDk;

                    BCBDk = BCx * BDy - BCy * BDx;

                    if (((BABDk > 0) && (BCBDk > 0)) || ((BABDk < 0) && (BCBDk < 0)))

                    {

                        returnResult = true;

                    }

                    else

                    {

                        returnResult = false;

                    }                   

                }

                else if ((BABCk == 0)||(BABDk==0))//點C或D在直線AB上

                {

                    double[] templine02Coords = new double[3];

                    if (BABCk == 0)//點C在直線AB上

                    {

                        templine02Coords[0] = line02Coords[0];

                        templine02Coords[1] = line02Coords[1];

                        templine02Coords[2] = line02Coords[2];

                    }

                    else//點D在直線AB上

        &