C#+AE 判断点是否在面内的方法

C#+AE 判断点是否在面内的方法

整体思路：射线法。
①：先判断点的X和Y坐标和多边形的Xmin,Xmax,Ymin,Ymax的关系。若超出了这四个值，则一定在多边形外；
②：若不符合上述条件，则继续。向左做线段，线段的左顶点的X坐标值一定要小于Xmin。然后判断线段和多边形的交点；
若交点为偶数个，则在多边形外；若交点为奇数个，则点在多边形内；
③：因为最后取的交点是按照Ipolyline和多边形Polygon作得拓扑关系的交集，交集是IGeometry对象，其向IgeometryCollection对象跳转，最后得到一个点击IpointCollection，根据PointCount属性可得到相交点的个数。

得到最小X坐标值的函数：

public double getXMinValue(IPolygon nPolygon)

{

IPolygon sPolygon;

sPolygon = nPolygon;

IPointCollection pPointCollection;

pPointCollection = sPolygon as IPointCollection;

int n = pPointCollection.PointCount;

double[] coordX = new double
;

for (int i = 0; i < n; i++)

{

IPoint point = pPointCollection.get_Point(i);

coordX[i] = point.X;

}

//对数组进行从小到大排序

System.Array.Sort(coordX);

Xmin = coordX[0];

return Xmin;

}

向左画射线并得到交点个数的代码：

try

{

ILine newLine = new LineClass();

IPoint toPoint = new PointClass();

toPoint.PutCoords(getXMinValue(pPolygon) - 20.0000000000000, pPoint.Y);

newLine.PutCoords(pPoint, toPoint);//给新的直线赋予起始坐标

//苗师兄想法

IPolyline l = new PolylineClass();

l.FromPoint = pPoint;

l.ToPoint = toPoint;

IGeometryCollection pPolyline = new PolylineClass();

ISegmentCollection pPath;

pPath = new PathClass();

object missing1 = Type.Missing;

object missing2 = Type.Missing;

pPath.AddSegment(newLine as ISegment, ref missing1, ref missing2);

pPolyline.AddGeometry(pPath as IGeometry, ref missing1, ref missing2);

IElement element = DrawLineSymbol(pPolyline as IGeometry, pColor);

pGraph.AddElement(element, 0);

pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);

ITopologicalOperator pTopo = pPolygon as ITopologicalOperator;//pPolygon多边形

IGeometryCollection pGeoCol = pTopo.Intersect((IGeometry)l, esriGeometryDimension.esriGeometry0Dimension) as IGeometryCollection; //执行到这一句有问题；

IPointCollection pPointCol = pGeoCol as IPointCollection;

if ((pPointCol.PointCount) % 2 == 0)

{

MessageBox.Show("射线和多边形的交点个数为："+pPointCol.PointCount.ToString()+",点在多边形外。");

}

else

{

MessageBox.Show("射线和多边形的交点个数为："+pPointCol.PointCount.ToString()+",点在多边形内。");

}

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

本文是按照Polygon对象考虑的面，所以并未考虑重叠面的问题。