WorldWind学习系列四：功能分析——Show Planet Axis、Show Position 、Show Cross Hairs功能
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();
}
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();
}
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();
}
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
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