WorldWind系列十二：Measure插件学习.doc

WorldWind系列十二：Measure插件学习（上）来源：博客园 作者：无痕客我在写自己的WorldWind插件时，遇到很大挫折，上周六本来想写个简单的画线的插件，费了九牛二虎之力终于画出了，如何以动画效果画出线的问题没解决。Direct3D中画线本来是个简单的事，画到球面上也不难，但是实践告诉我：我前期学习WW，又犯了眼高手低的毛病！改动人家写好的插件代码容易，但要把插件的整个流程都自己写，就没想象的简单啦，写代码不严谨的小问题就不说了，我周六画线的主要问题是Direct3D编程都浮在表面，连PrimitiveType中各类型的基元数和顶点的关系没搞清楚。（如想了解请参看：/wuhenke/archive/2009/12/27/1633411.html红色部分）自己在画线上体验，让我决定先学习Measure插件。另外，我一直想做个类似VE插件，支持加载ArcGIS切图方式的影像，自己想了很久，有几个主要困惑没解决：投影方式不同如何处理、只要部分影像（如何计算行列数）、切图的中心问题（VE影像是全球的，切图中心经纬度为（0,0）等等。所以，前段WW实践，让我很受打击，博客就没心情更新啦！虽然理论和实践还有很大的距离，但是总结还是很重要的！上面都是题外话了，开始说说Measure插件吧！总体感觉Measure插件很强大，如果能搞清楚，在球面上画点、线、面都不是难事啦。（前提：要有点DirectX编程基础）MeasureTool.cs中有两个大类：MeasureTool(插件类)和MeasureToolLayer(渲染对象类)。MeasureToolLayer类中又包含五个内部类：MeasureLine、MeasureMultiLine 、MeasurePropertiesDialog、 MeasureState 、SaveMultiLine（如下图）MeasureTool作为插件类，需要实现Load() 和Unload()方法，不详说。Load()中注册了一些事件。加载代码publicoverridevoidLoad()/构造渲染对象layer=newMeasureToolLayer(this,ParentApplication.WorldWindow.DrawArgs);/设置纹理路径layer.TexturePath=Path.Combine(PluginDirectory,PluginsMeasure);ParentApplication.WorldWindow.CurrentWorld.RenderableObjects.Add(layer);menuItem=newMenuItem(MeasuretM);menuItem.Click+=newEventHandler(menuItemClicked);ParentApplication.ToolsMenu.MenuItems.Add(menuItem);/Subscribeevents 注册了事件ParentApplication.WorldWindow.MouseMove+=newMouseEventHandler(layer.MouseMove);ParentApplication.WorldWindow.MouseDown+=newMouseEventHandler(layer.MouseDown);ParentApplication.WorldWindow.MouseUp+=newMouseEventHandler(layer.MouseUp);ParentApplication.WorldWindow.KeyUp+=newKeyEventHandler(layer.KeyUp);MeasureToolLayer作为渲染对象类，是WW插件实现的重点。必须重载的方法Initialize（）、Update（）、Render（）和PerformSelectionAction(DrawArgs drawArgs)。我们先分别看看MeasureToolLayer的五个内部类。public enum MeasureStateIdle,Measuring,CompleteMeasureState是个枚举类型，存放Measure的当前状态的（空闲、测量中、完成）。从上图中，我们可看到MeasurePropertiesDialog和 SaveMultiLine类。MeasurePropertiesDialog继承自Form,主要是设置画线的类型：单线、多条线。设置MeasureMode代码privatevoidokButton_Click(objectsender,EventArgse)if(lineModeButton.Checked=true)World.Settings.MeasureMode=MeasureMode.Single;elseWorld.Settings.MeasureMode=MeasureMode.Multi;this.Close();SaveMultiLine类基础自Form。主要实现将画出的多线，保存为KML或Shp格式。保存代码privatevoidsaveButton_Click(objectsender,System.EventArgse)/Heh.SaveFileDialogchooser=newSaveFileDialog();chooser.DefaultExt=*.csv;chooser.Filter=kmlfiles(*.kml)|*.kml|Shapefiles(*.shp)|*.shp;chooser.Title=SaveMultiline;chooser.ShowDialog(MainApplication.ActiveForm);Stringfilename=chooser.FileName;Console.WriteLine(filename);tryif(filename.EndsWith(.kml)StreamWriterwriter=newStreamWriter(filename);stringkml=writeKML();writer.WriteLine(kml);writer.Close();/needtobeabletosavetoanetworkashapefileaccessibleif(filename.EndsWith(.shp)writeShape(filename);catch(Exceptionex)MessageBox.Show(ex.Message);输出KML文件代码；KML代码privatestringwriteKML()/constructXMLtosendXmlDocumentdoc=newXmlDocument();XmlNodekmlnode=doc.CreateElement(kml);XmlNodenode=doc.CreateElement(Placemark);XmlNodename=doc.CreateElement(name);name.InnerText=NewMeasurement;node.AppendChild(name);XmlNodedesc=doc.CreateElement(description);stringdescription=NewMeasurement;desc.InnerXml=description;node.AppendChild(desc);XmlNodepolygon=doc.CreateElement(Polygon);stringrequest=;foreach(MeasureLinelineinm_multiline)Doublelat=line.StartLatitude.Degrees;Doublelon=line.StartLongitude.Degrees;request+=lon+,+lat+,100n;request+=;polygon.InnerXml=request;node.AppendChild(polygon);kmlnode.AppendChild(node);doc.AppendChild(kmlnode);returndoc.OuterXml;保存为SHP格式文件代码保存为Shap代码privatevoidwriteShape(stringfilename)IntPtrshphandle=ShapeLib.SHPCreate(filename,ShapeLib.ShapeType.PolyLine);doublelat=newdoublem_multiline.Count;doublelon=newdoublem_multiline.Count;inti=0;foreach(MeasureLinelineinm_multiline)lati=line.StartLatitude.Degrees;loni=line.StartLongitude.Degrees;i+;ShapeLib.SHPObjectpoly=ShapeLib.SHPCreateSimpleObject(ShapeLib.ShapeType.Polygon,m_multiline.Count,lon,lat,null);ShapeLib.SHPWriteObject(shphandle,0,poly);ShapeLib.SHPDestroyObject(poly);ShapeLib.SHPClose(shphandle);上面是右键菜单的两个功能，如果实现添加右键菜单呢？很简单，MeasureToolLayer类只要重载RenderObject类的BuildContextMenu(ContextMenu menu)方法。示例代码如下：添加右键菜单代码/Fillsthecontextmenuwithmenuitemsspecifictothelayer./publicoverridevoidBuildContextMenu(ContextMenumenu)menu.MenuItems.Add(Properties,newSystem.EventHandler(OnPropertiesClick);menu.MenuItems.Add(SaveMulti-PointLine,newSystem.EventHandler(saveLine);OnPropertiesClick和saveLine就是用来调用两个窗体类的。MeasureMultiLine继承自ArrayList，主要是存放MeasureLine的集合。internalclassMeasureMultiLine:ArrayList/添加线publicvoidaddLine(MeasureLineline)Add(line);/删除最后一条线publicvoiddeleteLine()RemoveAt(Count-1);/计算集合中线的总长度，我们关注如何计算单条线的长度。publicdoublegetLength()doublesum=0.0;foreach(MeasureLinelineinthis)sum+=line.Linear;returnsum;/线集合的渲染方法。publicvoidRender(DrawArgsdrawArgs)foreach(MeasureLinelineinthis)try/调用线的渲染方法line.Render(drawArgs);catchMeasureLine继承自ListViewItem，是该Measure插件的关键部分，主要是对线对象的计算和部分渲染。这里面知识点比较重要，很多可以被我们借鉴重用。其中用到的重要方法Calculate() 和Render()，还有一些没用到的方法（这里暂不分析）。publicvoidCalculate(Worldworld,booluseTerrain)/计算球面上两点间圆弧（对应的角度）AngleangularDistance=World.ApproxAngularDistance(startLatitude,startLongitude,endLatitude,endLongitude);/计算圆弧长度=弧度值*半径Linear=angularDistance.Radians*world.EquatorialRadius;/每两度一个点（下面计算不是好理解，但是我们可以借鉴的重点）/ 2的弧度为 （2*PI/180）即约等于 2*3/180=1/30;(作者将PI取整为3啦)/每两度一个点：samples=(int)(angularDistance.Radians/2度的弧度值);/即samples=(int)(angularDistance.Radians/(1/30);intsamples=(int)(angularDistance.Radians*30);/1pointforevery2degrees.if(samples2)samples=2;/构建点集合（线中取samples个点）LinearTrackLine=newCustomVertex.PositionColoredsamples;for(inti=0;iLinearTrackLine.Length;i+)LinearTrackLinei.Color=World.Settings.MeasureLineLinearColorXml;Anglelat,lon=Angle.Zero;for(inti=0;i0)label+=FormatDistance(groundTrack)+Units;elselabel+=FormatDistance(linearDistance)+Units;/在线的中点处画出线段长度（DrawText将文字渲染到球面上某点）drawArgs.defaultDrawingFont.DrawText(null,label,(int)labelXy.X,(int)labelXy.Y,World.Settings.MeasureLineLinearColor);上面代码画出的线和长度，在任何缩放级别下都是可见的，不是太好。下面是我借鉴VE插件代码，实现了缩放级别控制，在一定级别下才显示线的长度。/判断缩放级别publicintGetZoomLevelByTrueViewRange(doubletrueViewRange)intmaxLevel=3;/视角范围为45度intminLevel=19;intnumLevels=minLevel-maxLevel+1;intretLevel=maxLevel;for(inti=0;inumLevels;i+)retLevel=i+maxLevel;doubleviewAngle=180;for(intj=0;j=viewAngle)break;returnretLevel;然后，在上面的Render()里添加控制条件 if (GetZoomLevelByTrueViewRange(drawArgs.WorldCamera.TrueViewRange.Degrees) 4) ，来控制长度的显示。添加层次控制publicvoidRender(DrawArgsdrawArgs)/Drawthemeasureline+endsVector3referenceCenter=newVector3(float)drawArgs.WorldCamera.ReferenceCenter.X,(float)drawArgs.WorldCamera.ReferenceCenter.Y,(float)drawArgs.WorldCamera.ReferenceCenter.Z);drawArgs.device.Transform.World=Matrix.Translation(-referenceCenter);if(World.Settings.MeasureShowGroundTrack&IsGroundTrackValid)drawArgs.device.DrawUserPrimitives(PrimitiveType.LineStrip,GroundTrackLine.Length-1,GroundTrackLine);drawArgs.device.DrawUserPrimitives(PrimitiveType.LineStrip,LinearTrackLine.Length-1,LinearTrackLine);drawArgs.device.Transform.World=drawArgs.WorldCamera.WorldMatrix;if(GetZoomLevelByTrueViewRange(drawArgs.WorldCamera.TrueViewRange.Degrees)4)if(!drawArgs.WorldCamera.ViewFrustum.ContainsPoint(WorldXyzMid)/Labelisinvisiblereturn;Vector3labelXy=drawArgs.WorldCamera.Project(WorldXyzMid-referenceCenter);stringlabel=;/=Text;if(groundTrack0)label+=FormatDistance(groundTrack)+Units;elselabel+=FormatDistance(linearDistance)+Units;drawArgs.defaultDrawingFont.DrawText(null,label,(int)labelXy.X,(int)labelXy.Y,World.Settings.MeasureLineLinearColor);下面我们看一下MeasureToolLayer类。代码publicoverridevoidRender(DrawArgsdrawArgs)if(!isOn)return;/Turnofflightif(World.Settings.EnableSunShading)drawArgs.device.RenderState.Lighting=false;/Checkthattexturesareinitialisedif(!isInitialized)Initialize(drawArgs);if(DrawArgs.MouseCursor=CursorType.Arrow)/Useourcursorwhenthemouseisntoverotherelementsrequiringdifferentcursor/使用自己的鼠标类型（可以借鉴学习）DrawArgs.MouseCursor=CursorType.Measure;if(State=MeasureState.Idle)return;/稍后分析if(!CalculateRectPlacement(drawArgs)return;if(Distance1,endPoint);*/绘制线集合multiline.Render(drawArgs);/Drawtheinforect /赋予纹理device.TextureState0.ColorOperation=TextureOperation.SelectArg1;device.SetTexture(0,m_texture);device.VertexFormat=CustomVertex.TransformedColoredTextured.Format;/绘制矩形（由两个三角形构成）device.DrawUserPrimitives(PrimitiveType.TriangleStrip,2,rect);device.TextureState0.ColorOperation=TextureOperation.Disable;/绘制连接线（三个点）device.DrawUserPrimitives(PrimitiveType.LineStrip,2,rectLineConnection);/绘制矩形边框device.DrawUserPrimitives(PrimitiveType.LineStrip,rectFrame.Length-1,rectFrame);/渲染绘制矩形上的文字drawArgs.defaultDrawingFont.DrawText(null,labelText,labelTextRect,DrawTextFormat.None,0xff24);device.RenderState.ZBufferEnable=true;if(World.Settings.EnableSunShading)drawArgs.device.RenderState.Lighting=true;光标问题DrawArgs.cs中CursorType中所有光标类型。/ / Mouse cursor/ public enum CursorTypeArrow = 0,Hand,Cross,Measure,SizeWE,SizeNS,SizeNESW,SizeNWSE更新光标方法340行更新光标代码publicvoidUpdateMouseCursor(System.Windows.Forms.Controlparent)if(lastCursor=mouseCursor)return;switch(mouseCursor)caseCursorType.Hand:parent.Cursor=System.Windows.Forms.Cursors.Hand;break;caseCursorType.Cross:parent.Cursor=System.Windows.Forms.Cursors.Cross;break;caseCursorType.Measure:if(measureCursor=null)/从外界加载光标measureCursor=ImageHelper.LoadCursor(measure.cur);parent.Cursor=measureCursor;