今天主要看了Show Planet Axis、Show Position 、Show Cross Hairs功能，主要是它们在菜单调用方式上都是很类似。代码如下：
显示位置信息 private void menuItemShowPosition_Click( object sender, System.EventArgs e) { World.Settings.ShowPosition = ! World.Settings.ShowPosition; this .toolBarButtonPosition.Pushed = World.Settings.ShowPosition; this .menuItemShowPosition.Checked = World.Settings.ShowPosition; this .worldWindow.Invalidate(); }// 显示中心十字标 private void menuItemShowCrosshairs_Click( object sender, System.EventArgs e) { // 控制中心十字标显示与否 World.Settings.ShowCrosshairs = ! World.Settings.ShowCrosshairs; this .menuItemShowCrosshairs.Checked = World.Settings.ShowCrosshairs; this .worldWindow.Invalidate(); }
从上面的代码看，我们只能惊叹代码封装的很好，同样都调用this.worldWindow.Invalidate();难道Invalidate()函数万能？！请参考我的Invalidate()方法学习（资料收集），原来该方法是界面区域失效，发送了重绘事件，将会调用WorldWindow.cs中重载了的OnPaint（）。OnPaint方法里主要是调用了 Render()方法。所以我们的关键是看Render()中如何实现上面三个功能。（其实Render()中实现的功能很多，主要是控制界面绘制方面的，以后还会提到它的）
Render()实现上面三个功能也大量使用了DirectX和Direct 3D方面的知识,请网上搜索学习相关知识或参看我的Direct3D学习（资料收集）。
显示中心十字线功能
Render()中实现代码为
787行 if (World.Settings.ShowCrosshairs) this.DrawCrossHairs();
实现显示十字标代码 实现显示十字标代码 protected void DrawCrossHairs() { int crossHairSize = 10 ; if ( this .crossHairs == null ) { crossHairs = new Line(m_Device3d); // 构造线对象 } Vector2[] vertical = new Vector2[ 2 ]; Vector2[] horizontal = new Vector2[ 2 ]; // Vector2[] test = new Vector2[2]; // 这是我试验添加的，效果请看下面的截图 horizontal[ 0 ].X = this .Width / 2 - crossHairSize; horizontal[ 0 ].Y = this .Height / 2 ; horizontal[ 1 ].X = this .Width / 2 + crossHairSize; horizontal[ 1 ].Y = this .Height / 2 ; vertical[ 0 ].X = this .Width / 2 ; vertical[ 0 ].Y = this .Height / 2 - crossHairSize; vertical[ 1 ].X = this .Width / 2 ; vertical[ 1 ].Y = this .Height / 2 + crossHairSize; // test[0].X = this.Width / 2; // test[0].Y = this.Height / 2 + crossHairSize; // test[1].X = this.Width / 2 + crossHairSize; // test[1].Y = this.Height / 2; crossHairs.Begin(); crossHairs.Draw(horizontal, crossHairColor); crossHairs.Draw(vertical, crossHairColor); // crossHairs.Draw(test,Color.Red.ToArgb()); crossHairs.End(); }
上面注销部分（我加了红线）是我试验添加的，效果请看上面的截图。其实就是划几条两点之间的线。
显示位置信息
是在Render()中调用RenderPositionInfo()方法的，请看该段实现代码。
实现显示位置坐标信息 private const int positionAlphaStep = 20 ; private int positionAlpha = 255 ; private int positionAlphaMin = 40 ; private int positionAlphaMax = 205 ; protected void RenderPositionInfo() { // Render some Development information to screen string captionText = _caption; captionText += " \n " + this .drawArgs.UpperLeftCornerText; if (World.Settings.ShowPosition) { string alt = null ; double agl = this .drawArgs.WorldCamera.AltitudeAboveTerrain; /* if(agl>100000) alt = string.Format("{0:f2}km", agl/1000); else alt = string.Format("{0:f0}m", agl); */ alt = ConvertUnits.GetDisplayString(agl); string dist = null ; double dgl = this .drawArgs.WorldCamera.Distance; /* if(dgl>100000) dist = string.Format("{0:f2}km", dgl/1000); else dist = string.Format("{0:f0}m", dgl); */ dist = ConvertUnits.GetDisplayString(dgl); // Heading from 0 - 360 double heading = this .drawArgs.WorldCamera.Heading.Degrees; if (heading < 0 ) heading += 360 ; // 构造显示位置坐标信息字符串 captionText += String.Format( " Latitude: {0}\nLongitude: {1}\nHeading: {2:f2}\nTilt: {3}\nAltitude: {4}\nDistance: {5}\nFOV: {6} " , this .drawArgs.WorldCamera.Latitude, this .drawArgs.WorldCamera.Longitude, heading, this .drawArgs.WorldCamera.Tilt, alt, dist, this .drawArgs.WorldCamera.Fov ); if (agl < 300000 ) { captionText += String.Format( " \nTerrain Elevation: {0:n} meters\n " , this .drawArgs.WorldCamera.TerrainElevation); } } if ( this .showDiagnosticInfo) captionText += " \nAvailable Texture Memory: " + (m_Device3d.AvailableTextureMemory / 1024 ).ToString( " N0 " ) + " kB " + " \nBoundary Points: " + this .drawArgs.numBoundaryPointsRendered.ToString() + " / " + this .drawArgs.numBoundaryPointsTotal.ToString() + " : " + this .drawArgs.numBoundariesDrawn.ToString() + " \nTiles Drawn: " + ( this .drawArgs.numberTilesDrawn * 0.25f ).ToString() + " \n " + this .drawArgs.WorldCamera + " \nFPS: " + this .fps.ToString( " f1 " ) + " \nRO: " + m_World.RenderableObjects.Count.ToString( " f0 " ) + " \nmLat: " + this .cLat.Degrees.ToString() + " \nmLon: " + this .cLon.Degrees.ToString() + " \n " + TimeKeeper.CurrentTimeUtc.ToLocalTime().ToLongTimeString(); captionText = captionText.Trim(); // 定义要画出文本的样式 DrawTextFormat dtf = DrawTextFormat.NoClip | DrawTextFormat.WordBreak | DrawTextFormat.Right; int x = 7 ; int y = _menuBar != null && World.Settings.ShowToolbar ? 65 : 7 ; // 定义盛放位置文本的矩形框 Rectangle textRect = Rectangle.FromLTRB(x,y, this .Width - 8 , this .Height - 8 ); // 我添加的测试用代码 Rectangle testRect = Rectangle.FromLTRB(x, y, this .Width, this .Height); // Hide position info when toolbar is open if (_menuBar.IsActive) // 如果上面的_menuBar处于活动状态，则更改位置文本的Alpha值 { positionAlpha -= positionAlphaStep; if (positionAlpha < positionAlphaMin) { positionAlpha = positionAlphaMin; } } else { positionAlpha += positionAlphaStep; if (positionAlpha > positionAlphaMax) positionAlpha = positionAlphaMax; } int positionBackColor = positionAlpha << 24 ; int positionForeColor = ( int )(( uint )(positionAlpha << 24 ) + 0xffffffu ); 使用Font对象defaultDrawingFont的DrawText（）实现绘制位置信息 this .drawArgs.defaultDrawingFont.DrawText( null , captionText, textRect, dtf, positionBackColor); textRect.Offset( - 1 , - 1 ); this .drawArgs.defaultDrawingFont.DrawText( null , captionText, textRect, dtf, positionForeColor); // 下面这行是我添加的，测试用 this .drawArgs.defaultDrawingFont.DrawText( null , " 无痕客在研究WorldWind应用！ " , textRect, dtf,Color.Red.ToArgb()); }上面需要注意的知识点就是：使用Font对象（实例：defaultDrawingFont）的DrawText（）实现绘制文本信息。
地球轴线绘制
WorldWindow.cs的Render()方法中调用了World.cs中Render()方法，该方法又调用了DrawAxis（）
方
法实现地球轴线绘制。
453行 if (Settings.showPlanetAxis)
this.DrawAxis(drawArgs); 画地球轴线 private void DrawAxis(DrawArgs drawArgs) { CustomVertex.PositionColored[] axis = new CustomVertex.PositionColored[ 2 ]; Vector3 topV = MathEngine.SphericalToCartesian( 90 , 0 , this .EquatorialRadius + 0.15f * this .EquatorialRadius); axis[ 0 ].X = topV.X; axis[ 0 ].Y = topV.Y; axis[ 0 ].Z = topV.Z; axis[ 0 ].Color = System.Drawing.Color.Pink.ToArgb(); Vector3 botV = MathEngine.SphericalToCartesian( - 90 , 0 , this .EquatorialRadius + 0.15f * this .EquatorialRadius); axis[ 1 ].X = botV.X; axis[ 1 ].Y = botV.Y; axis[ 1 ].Z = botV.Z; axis[ 1 ].Color = System.Drawing.Color.Pink.ToArgb(); drawArgs.device.VertexFormat = CustomVertex.PositionColored.Format; drawArgs.device.TextureState[ 0 ].ColorOperation = TextureOperation.Disable; drawArgs.device.Transform.World = Matrix.Translation( ( float ) - drawArgs.WorldCamera.ReferenceCenter.X, ( float ) - drawArgs.WorldCamera.ReferenceCenter.Y, ( float ) - drawArgs.WorldCamera.ReferenceCenter.Z ); drawArgs.device.DrawUserPrimitives(PrimitiveType.LineStrip, 1 , axis); drawArgs.device.Transform.World = drawArgs.WorldCamera.WorldMatrix; }
其他部分：
WorldWind学习系列三：简单功能分析——主窗体的键盘监听处理及拷贝和粘贴位置坐标功能
WorldWind学习系列三：功能分析——截屏功能和“关于”窗体分析
WorldWind学习系列二：擒贼先擒王篇2
WorldWind学习系列二：擒贼先擒王篇1
WorldWind学习系列一：顺利起航篇
转载于:https://www.cnblogs.com/wuhenke/archive/2009/12/12/1622752.html
相关资源：数据结构—成绩单生成器