手工画扇型(3)

如何得到扇型的数据，这其中需要考虑角度在180时，和小于180两种情况。
得到数据可以利用mo的Extent得到矩形覆盖范围，该方位是借助圆心，和半径画出矩形，先得到该矩形区域的值。
该区域中的任意值和半径边，变化边的角度，如果两角度相加等于张角，而且到圆心的距离小等于半径，那么该点在所选区域内。
对于180的，可以利用斜率来算，因为先前已经保存了半径在哪以象限

       /// <summary>
       /// get sector region data  for gridbase
       /// </summary>
       /// <param name="FeatureList">ractangle region</param>
       /// <param name="unitExtent">longth</param>
       /// <returns></returns>
       public SelectedData SetGridBaseSelectedData(ArrayList FeatureList, double unitExtent)
       {
           SelectedData dt = new SelectedData();

           ESRI.MapObjects2.Core.Point pt = new ESRI.MapObjects2.Core.PointClass();
     
           double thirdDist = Math.Sqrt(Math.Pow((varietyPoint.X - firstPoint.X),2) + Math.Pow((varietyPoint.Y - firstPoint.Y),2));

           try
           {

               for(int i = 0;i<FeatureList.Count;i++)
               {
              .//get pt

//                   int length = Convert.ToInt32(Math.Sqrt(Math.Pow((pt.X - firstPoint.X),2) + Math.Pow((pt.Y - firstPoint.Y),2)));
                  double lengthDist = Math.Sqrt(Math.Pow((pt.X - firstPoint.X),2) + Math.Pow((pt.Y - firstPoint.Y),2));

                   if (Convert.ToInt32(lengthDist) <= Convert.ToInt32(this.radius))    // reduce errors
                   {
                       if (Convert.ToInt32(Math.Abs(sweepAngle)) == 180)
                       {
                           //two point connection line is y = ax+b.   a= (y1-y2)/(x1-x2) 
                           double a1 = (firstPoint.Y - secondPoint.Y) / (firstPoint.X - secondPoint.X);
                           double b1 = (firstPoint.Y - a1*firstPoint.X);

                           double varietyB = 0.0d, movePro =0.0d;

                           //know the radius direction
                           switch(radiusDirection)
                           {
                               case 1: 
                               case 4:   
                                   //direction must down. y=ax+b . the line move negative y1. 
                                   //know a and (x,y) to calculate b according to y=ax+b;
                                   varietyB = pt.Y - a1*pt.X ;
                                   movePro = b1 - varietyB;
                                   if (sweepAngle > 0)    //sweepAngle is 180
                                   {
                                       if (movePro >= 0)
                                       {
                                           .
                                       }
                                   }
                                   else       //sweepAngle is -180
                                   {
                                       if (movePro <= 0)
                                       {
                                           .
                                       }
                            
                                   }
                                   break;
                               case 2:
                               case 3:
                                   varietyB = pt.Y - a1*pt.X ;
                                   movePro = b1 - varietyB;
                                   if (sweepAngle > 0)
                                   {
                                       if (movePro <= 0)
                                       {
                                           .
                                       }
                                   }
                                   else
                                   {
                                       if (movePro >= 0)
                                       {
                                           
                                       }

                                   }
                                   break;
                               case 5:
                                   varietyB = firstPoint.X - pt.X ;
                                   if (sweepAngle > 0)
                                   {
                                       if (varietyB <=0)
                                       {
                                          
                                       }
                                   }
                                   else
                                   {
                                       if (varietyB >=0)
                                       {
                                           
                                       }

                                   }
                                   break;
                               case 6:
                                   varietyB = firstPoint.Y - pt.Y;
                                   if (sweepAngle > 0)
                                   {
                                       if (varietyB >=0)
                                       {
                                          
                                       }
                                   }
                                   else
                                   {
                                       if (varietyB <=0)
                                       {
                                          
                                       }

                                   }
                                   break;
                               case 7:
                                   varietyB = firstPoint.X - pt.X ;
                                   if (sweepAngle > 0)
                                   {
                                       if (varietyB >=0)
                                       {
                                           
                                       }
                                   }
                                   else
                                   {
                                       if (varietyB <=0)
                                       {
                                           
                                       }

                                   }

                                   break;
                               case 8:
                                   varietyB = firstPoint.Y - pt.Y;
                                   if (sweepAngle > 0)
                                   {
                                       if (varietyB >=0)
                                       {
                                          
                                       }
                                   }
                                   else
                                   {
                                       if (varietyB <=0)
                                       {
                                           
                                       }

                                   }

                                   break;
                           }
                       }
                       else     // sweepAngle must be less than 180.If any point and enother three point angle is equal to the angle, it is in the selection region.
                       {
                           // c*c = a*a + b*b - 2abcosα. 0<angle <180
                          double  anyRadiusDist = Math.Sqrt(Math.Pow((pt.X - secondPoint.X),2)+Math.Pow((pt.Y -secondPoint.Y),2));

                          double  anyVarietyDist = Math.Sqrt(Math.Pow((pt.X - varietyPoint.X),2)+Math.Pow((pt.Y - varietyPoint.Y),2));

                          float   angle1 = (float)(180*(Math.Acos((lengthDist*lengthDist + thirdDist*thirdDist -anyVarietyDist * anyVarietyDist) /(2*lengthDist*thirdDist)))/Math.PI);

                          float   angle2 =(float)(180*(Math.Acos((radius*radius + lengthDist*lengthDist - anyRadiusDist*anyRadiusDist)/(2*radius*lengthDist)))/Math.PI);

                          float   sumAngle = angle1 + angle2 ;

                           if (Convert.ToInt32(sumAngle) == Convert.ToInt32(Math.Abs(this.sweepAngle)))
                           {
                               
                           }
                       }
                   }
            
               }
               return dt;
           }
           catch
           {
               throw new Exception("Get gridbase of sector selection data failed.");
           }
       }

对于求扇型中心点可以借助方法dist = 2*r*sinA/(2*A) A是弧度
  

    /// <summary>
        /// Each side of the mid-point links to form center for sector of isosceles triangle.
        /// </summary>
        /// <returns></returns>
        public ESRI.MapObjects2.Core.Point SectorCenter()
        {
            
            double otherSideDist = 0.0d,sideDist=0.0d,a,b,c,check,n1;
            double k2 = 0.0d,k1=0.0d;

            if (Math.Abs(sweepAngle) > 179)
            {
                ESRI.MapObjects2.Core.Point centerP = new PointClass();
                otherSideDist = (4*this.Radius)/(3*Math.PI);

                if (radiusDirection == 5)
                {
                    if (sweepAngle > 0)     // right
                    {
                        centerP.X = firstPoint.X + otherSideDist;
                        centerP.Y = firstPoint.Y;
                    }
                    else
                    {
                        centerP.X = firstPoint.X - otherSideDist;
                        centerP.Y = firstPoint.Y;
                    }
                }
                else if (radiusDirection == 7)
                {
                    if (sweepAngle > 0)     // left
                    {
                        centerP.X = firstPoint.X - otherSideDist;
                        centerP.Y = firstPoint.Y;
                    }
                    else
                    {
                        centerP.X = firstPoint.X + otherSideDist;
                        centerP.Y = firstPoint.Y;
                    }
                }
                else if (radiusDirection == 6)
                {
                    if (sweepAngle > 0)     // bottom
                    {
                        centerP.X = firstPoint.X ;
                        centerP.Y = firstPoint.Y - otherSideDist;
                    }
                    else
                    {
                        centerP.X = firstPoint.X ;
                        centerP.Y = firstPoint.Y + otherSideDist;
                    }
                }
                else if(radiusDirection == 8)
                {
                    if (sweepAngle > 0)     // top
                    {
                        centerP.X = firstPoint.X ;
                        centerP.Y = firstPoint.Y + otherSideDist;
                    }
                    else
                    {
                        centerP.X = firstPoint.X ;
                        centerP.Y = firstPoint.Y - otherSideDist;
                    }
                }
                else
                {
                    k1 = (firstPoint.Y - secondPoint.Y) / (firstPoint.X - secondPoint.X);
                    k2 = (-1)/k1;
             
                    //(x-x1)*(x-x1)+(k2*x-n1)*(k2*x-n1)- r*r= 0

                    //(1+k2*k2)x*x-2(x1+k2*n1)*x +n1*n1+x1*x1-r*r=0

                    a = Math.Sqrt((otherSideDist*otherSideDist)/(1+k2*k2));

                    double x1 = a + this.firstPoint.X;

                    double y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;

                        //need know equation according to slope. y=ax+b
                        //calculte b
                    double varietySlope = y1 - k1*x1;

                    double centerSlope = firstPoint.Y - k1*x1;

                    double compare = centerSlope - varietySlope;

                    if (radiusDirection == 1 || radiusDirection ==4)
                    {
                        if (sweepAngle >0)
                        {
                            if (compare < 0)
                            {
                                x1 = (-a) + this.firstPoint.X;
                                y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;
                            }
                        }
                        else
                        {
                            if (compare > 0)
                            {
                                x1 = (-a) + this.firstPoint.X;
                                y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;
                            }
                        }
                    }
                    else if (radiusDirection == 2 || radiusDirection ==3)
                    {
                        if (sweepAngle > 0)
                        {
                            if (compare > 0)
                            {
                                x1 = (-a) + this.firstPoint.X;
                                y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;
                            }
                        }
                        else
                        {
                            if (compare < 0)
                            {
                                x1 = (-a) + this.firstPoint.X;
                                y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;
                            }
                        }
                    }

                        centerP.X = x1;
                        centerP.Y = y1;
                 }
                return centerP;
            }
            else  // sweepAngle is less than 179
            {

                //c*c = a*a + b*b - 2abcosα        a= radius/2 ,b= radius
                //  2*r*sinA/(3*A)  A represents radian.
                otherSideDist = (2*this.radius*Math.Sin(Math.Abs(sweepAngle)*Math.PI/360)*360)/(3*Math.Abs(sweepAngle)*Math.PI);

                sideDist = Math.Sqrt(otherSideDist*otherSideDist + this.radius*this.radius - 2* otherSideDist*radius*Math.Cos(Math.Abs(sweepAngle)*Math.PI/360));

                //y=ax+b
                //two point connection line is y = ax+b.   a= (y1-y2)/(x1-x2) 
                k1 = (firstPoint.Y - secondPoint.Y) / (firstPoint.X - secondPoint.X);
                double kv = (firstPoint.Y - varietyPoint.Y) / (firstPoint.X - varietyPoint.X);
                // k1<k2<kv

                //tana= |（k2-k1）/1-(k1k2)|  . y=ax+b

                //  k1+tana/(1+k1*tana)= k2 = (y1-y)/(x1-x) = (firstPoint.Y -y)/(firstPoint.X - x)

                
                double kn1 = (k1- Math.Tan(Math.Abs(sweepAngle)*Math.PI/360))/(1 + k1*Math.Tan(Math.Abs(sweepAngle)*Math.PI/360));
                double kn2 = (k1+ Math.Tan(Math.Abs(sweepAngle)*Math.PI/360))/(1 - k1*Math.Tan(Math.Abs(sweepAngle)*Math.PI/360));
                

                double kvn1 = (kv- Math.Tan(Math.Abs(sweepAngle)*Math.PI/360))/(1 + kv*Math.Tan(Math.Abs(sweepAngle)*Math.PI/360));
                 
                double kvn2 = (kv+ Math.Tan(Math.Abs(sweepAngle)*Math.PI/360))/(1 - kv*Math.Tan(Math.Abs(sweepAngle)*Math.PI/360));

                // this center must be in selection region.
                if (kn1.ToString("0.0000").CompareTo(kvn1.ToString("0.0000"))==0)
                {
                    k2 = kn1;
                }
                else if (kn1.ToString("0.0000").CompareTo(kvn2.ToString("0.0000"))==0)
                {
                    k2 = kn1;
                }
                else if (kn2.ToString("0.0000").CompareTo(kvn1.ToString("0.0000"))==0)
                {
                    k2 = kn2;
                }
                else if (kn2.ToString("0.0000").CompareTo(kvn2.ToString("0.0000"))==0)
                {
                    k2 = kn2;
                }

                // y = firstPoint.Y -k2 * firstPoint.X + k2*x
                 
                // (x-x1)*(x-x1)+(y-y1)*(y-y1) = r*r      (x1,y1) = (secondPoint.X,secondPoint.Y)

                n1 = firstPoint.Y- k2*firstPoint.X - secondPoint.Y ;
                //(x-x1)*(x-x1)+(k2*x-n1)*(k2*x-n1)- r*r= 0

                //(1+k2*k2)x*x-2(x1+k2*n1)*x +n1*n1+x1*x1-r*r=0

                a = 1+k2*k2;
                b = 2*(n1*k2 -secondPoint.X);

                c = secondPoint.X * secondPoint.X + n1*n1 -sideDist*sideDist;
 
                check = b*b - 4*a*c;

                if (check>=0)
                {
                    double x1 = (-b - Math.Sqrt(check))/(2*a);

                    double y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;

                    int otherLenDist = Convert.ToInt32(Math.Sqrt(Math.Pow((x1-firstPoint.X),2) + Math.Pow((y1-firstPoint.Y),2)));

                    int lenDist = Convert.ToInt32(Math.Sqrt(Math.Pow((x1-secondPoint.X),2) + Math.Pow((y1-secondPoint.Y),2)));
                
                    ESRI.MapObjects2.Core.Point centerP = new PointClass(); 

                    if ((otherLenDist == Convert.ToInt32(otherSideDist))&& (lenDist == Convert.ToInt32(sideDist)))
                    {
                        centerP.X = x1;
                        centerP.Y = y1;
                    }
                    else
                    {
                        x1 = (-b + Math.Sqrt(check))/(2*a);
                        y1 = firstPoint.Y - k2 * firstPoint.X +x1*k2;

                        centerP.X = x1;
                        centerP.Y = y1;
                    }
                    return centerP;
                }
                else
                {
                    return firstPoint; // return center point
                }
            }
             
         }