Geometry对象介绍.doc

ArcEngine Geometry库定义了基本几何图形的矢量表达形式，顶级的几何图形有Points、Multipoints、Polylines、Polygons、 Multipatches，Geodatabase和绘图系统使用这些几何图形来定义其他各种形状的特征和图形，提供了编辑图形的操作方法和地图符号系统符号化特征数据的途径。 Geometry库中几个核心类和接口构成了Geometry对象的基本框架。 GeometryEnvironment GeometryEnvironment提供了从不同的输入、设置或获取全局变量来创建几何图形的方法，以便控制geometry方法的行为。GeometryEnvironment对象是一个单例对象。publicIPolylineTestGeometryEnvironment()ISpatialReferenceFactoryspatialReferenceFactory=newSpatialReferenceEnvironmentClass();/Createaprojectedcoordinatesystemanddefineitsdomain,resolution,andx,ytolerance.ISpatialReferenceResolutionspatialReferenceResolution=spatialReferenceFactory.CreateProjectedCoordinateSystem(int)esriSRProjCSType.esriSRProjCS_NAD1983UTM_11N)asISpatialReferenceResolution;spatialReferenceResolution.ConstructFromHorizon();ISpatialReferenceTolerancespatialReferenceTolerance=spatialReferenceResolutionasISpatialReferenceTolerance;spatialReferenceTolerance.SetDefaultXYTolerance();ISpatialReferencespatialReference=spatialReferenceResolutionasISpatialReference;/CreateanarrayofWKSPointstructuresstartinginthemiddleofthex,ydomainofthe/projectedcoordinatesystem.doublexMin;doublexMax;doubleyMin;doubleyMax;spatialReference.GetDomain(outxMin,outxMax,outyMin,outyMax);doublexFactor=(xMin+xMax)*0.5;doubleyFactor=(yMin+yMax)*0.5;WKSPointwksPoints=newWKSPoint10;for(inti=0;iwksPoints.Length;i+)wksPointsi.X=xFactor+i;wksPointsi.Y=yFactor+i;IPointCollection4pointCollection=newPolylineClass();IGeometryBridge2geometryBridge=newGeometryEnvironmentClass();geometryBridge.AddWKSPoints(pointCollection,refwksPoints);IPolylinepolyline=pointCollectionasIPolyline;polyline.SpatialReference=spatialReference;returnpolyline; new GeometryEnvironmentClass仅仅是创建了一个指向已存在的GeometryEnvironmentClass的引用。注意 IGeometryBridge2接口的使用，addWKSPoints方法将WKSPoint二维点添加到PointCollection中，用于构建 path、ring、polyline、polygon，或增加新点到Multipoint、TriangleFan、TriangleStrip。在 Geometry库中，除了IGeometryBridge2还有IGeometryBridge接口，后者继承了前者，增加了一些编辑功能（添加点、插入点、重置点、分段等）。 GeometryBag GeometryBag是支持IGeometry接口的几何对象引用的集合，任何几何对象都可以通过IGeometryCollection接口添加到 GeometryBag中，但是在使用拓扑操作的时候，需要注意不同类型的几何类型可能会有相互不兼容的情况。在向GeometryBag中添加几何对象的时候，GeometryBag对象需要指定空间参考，添加到其中的几何对象均拥有和GeometryBag对象一样的空间参考。privateIPolygonGeometryBag_Example(IFeatureClassfeatureClass)/Checkinputobjects.if(featureClass=null)returnnull;IGeoDatasetgeoDataset=featureClassasIGeoDataset;ISpatialFilterqueryFilter=newSpatialFilterClass();/Setthepropertiesofthespatialfilterhere.IGeometrygeometryBag=newGeometryBagClass();/Definethespatialreferenceofthebagbeforeaddinggeometriestoit.geometryBag.SpatialReference=geoDataset.SpatialReference;/Useanonrecyclingcursorsoeachreturnedgeometryisaseparateobject.IFeatureCursorfeatureCursor=featureClass.Search(queryFilter,false);IGeometryCollectiongeometryCollection=geometryBagasIGeometryCollection;IFeaturecurrentFeature=featureCursor.NextFeature();while(currentFeature!=null)/Addareferencetothisfeaturesgeometryintothebag./Youdontspecifythebeforeoraftergeometry(missing),/sothecurrentFeature.ShapeIGeometryisaddedtotheendofthegeometryCollection.objectmissing=Type.Missing;geometryCollection.AddGeometry(currentFeature.Shape,refmissing,refmissing);currentFeature=featureCursor.NextFeature();/Createthepolygonthatwillbetheunionofthefeaturesreturnedfromthesearchcursor./Thespatialreferenceofthisfeaturedoesnotneedtobesetaheadoftime.The/ConstructUnionmethoddefinestheconstructedpolygonsspatialreferencetobethesameas/theinputgeometrybag.ITopologicalOperatorunionedPolygon=newPolygonClass();unionedPolygon.ConstructUnion(geometryBagasIEnumGeometry);returnunionedPolygonasIPolygon; Points 一个点包括X、Y坐标，同时可以增加M、Z值及ID属性来扩展点的功能。 Multipoints 点的集合，多点组成Multipoint几何类型，使用multipoint对象实现了的IPointCollection接口可以访问所有的点元素，这些点同样可以拥有M、Z值及ID属性来获得更多的地理空间内涵。 下面列举一个例子，通过一个已知的polyline来定义一个新的multipart polyline。publicIPolylineConstructMultiPartPolyline(IPolylineinputPolyline)IGeometryoutGeometry=newPolylineClass();/Alwaysassociatenew,top-levelgeometrieswithanappropriatespatialreference.outGeometry.SpatialReference=inputPolyline.SpatialReference;IGeometryCollectiongeometryCollection=outGeometryasIGeometryCollection;ISegmentCollectionsegmentCollection=inputPolylineasISegmentCollection;/Iterateoverexistingpolylinesegmentsusingasegmentenumerator.IEnumSegmentsegments=segmentCollection.EnumSegments;ISegmentcurrentSegment;intpartIndex=0;intsegmentIndex=0;segments.Next(outcurrentSegment,refpartIndex,refsegmentIndex);while(currentSegment!=null)ILinenormal=newLineClass();/Geometrymethodswith_Query_intheirnameexpecttomodifyexistinggeometries./Inthiscase,theQueryNormalmethodmodifiesanexistingline/segment(normal)tobethenormalvectorto/currentSegmentatthespecifiedlocationalongcurrentSegment.currentSegment.QueryNormal(esriSegmentExtension.esriNoExtension,0.5,true,currentSegment.Length/3,normal);/Sinceeachnormalvectorisnotconnectedtoothers,createanewpathforeachone.ISegmentCollectionnewPath=newPathClass();objectmissing=Type.Missing;newPath.AddSegment(normalasISegment,refmissing,refmissing);/ThespatialreferenceassociatedwithgeometryCollectionwillbeassignedtoallincomingpathsandsegments.geometryCollection.AddGeometry(newPathasIGeometry,refmissing,refmissing);segments.Next(outcurrentSegment,refpartIndex,refsegmentIndex);/ThegeometryCollectionnowcontainsthenew,multipartpolyline.returngeometryCollectionasIPolyline; ISegment接口的QueryNormal方法用来在弧段上的某一点生成该弧段的法线，指定其长度，这样就生成了新的segment，并且多个path添加到geometryCollection中，以IPolyline的形式返回。 Polylines Polylines是有序path组成的集合，可以拥有M、Z和ID属性值。Polyline对象的IPointCollection接口包含了所有节点的复制，IGeometryCollection接口可以获取polyline的paths，ISegmentCollection接口可以获取 polyline的segments。 Polyline结构图 Polygons Polygon是一系列rings组成的集合，可以拥有M、Z和ID属性值。每一个ring由一个或多个segment组成，Polygon或ring对象的IPointCollection接口包含了所有节点的复制，IGeometryCollection接口可以获取polygon的rings， ISegmentCollection接口可以获取polygon的segments。 Polygon结构图 Multipatch Multipatch用于描述3D面状几何类型，由一系列的矢量三角形构成，如果其中的part是一个ring，那么它必须是封闭的，第一个节点和最后一个节点相同，另外每个part所包含节点的顺序非常重要，Inner Rings在Outer Rings之后，代表单个表面patch的一系列rings必须由第一个ring开始。在9.0以后的开发包中，使用IGeneralMultiPatchCreator创建新的Multipatch，IGeometryMaterial进行材质贴图。publicIMultiPatchCreateMultipatch()/Preparethegeometrymateriallist.IGeometryMaterialtexture=newGeometryMaterialClass();texture.TextureImage=C:TempMyImage.bmp;IGeometryMaterialListmaterialList=newGeometryMaterialListClass();materialList.AddMaterial(texture);/Createthemultipatch.IGeneralMultiPatchCreatormultiPatchCreator=newGeneralMultiPatchCreatorClass();multiPatchCreator.Init(4,1,false,false,false,4,materialList);/Setuppart./CouldalsouseaRingoraTriangleFan.multiPatchCreator.SetPatchType(0,esriPatchType.esriPatchTypeTriangleStrip);multiPatchCreator.SetMaterialIndex(0,0);multiPatchCreator.SetPatchPointIndex(0,0);multiPatchCreator.SetPatchTexturePointIndex(0,0);/Setreal-worldpoints.WKSPointZupperLeft=newWKSPointZ();WKSPointZlowerLeft=newWKSPointZ();WKSPointZupperRight=newWKSPointZ();WKSPointZlowerRight=newWKSPointZ();upperLeft.X=0;upperLeft.Y=0;upperLeft.Z=0;upperRight.X=300;upperRight.Y=0;upperRight.Z=0;lowerLeft.X=0;lowerLeft.Y=0;lowerLeft.Z=-100;lowerRight.X=300;lowerRight.Y=1;lowerRight.Z=-100;multiPatchCreator.SetWKSPointZ(0,refupperRight);multiPatchCreator.SetWKSPointZ(1,reflowerRight);multiPatchCreator.SetWKSPointZ(2,re