WorldWind學習系列四：功能分析——Show Planet Axis、Show Position 、Show Cross Hairs功能

原文轉自：http://www.cnblogs.com/wuhenke/archive/2009/12/12/1622752.html

今天主要看了Show Planet Axis、Show Position 、Show Cross Hairs功能，主要是它們在菜單調用方式上都是很類似。代碼如下：

Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->顯示位置信息 
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();
        }

 

Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> //顯示中心十字標   
 private void menuItemShowCrosshairs_Click(object sender, System.EventArgs e)
        {
　　　　　　　//控制中心十字標顯示與否
            World.Settings.ShowCrosshairs = !World.Settings.ShowCrosshairs;
            this.menuItemShowCrosshairs.Checked = World.Settings.ShowCrosshairs;
            this.worldWindow.Invalidate();
        }

從上面的代碼看，我們只能驚歎代碼封裝的很好，同樣都調用this.worldWindow.Invalidate();難道Invalidate()函數萬能？！請參考我的Invalidate()方法學習（資料收集），原來該方法是界面區域失效，發送了重繪事件，將會調用WorldWindow.cs中重載了的OnPaint（）。OnPaint方法裏主要是調用了 Render()方法。所以我們的關鍵是看Render()中如何實現上面三個功能。（其實Render()中實現的功能很多，主要是控制界面繪製方面的，以後還會提到它的）

     Render()實現上面三個功能也大量使用了DirectX和Direct 3D方面的知識,請網上搜索學習相關知識或參看我的Direct3D學習（資料收集）。

    顯示中心十字線功能

　　Render()中實現代碼爲

      787行     if (World.Settings.ShowCrosshairs)
                    this.DrawCrossHairs();

實現顯示十字標代碼 




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-->實現顯示十字標代碼 

        protected void DrawCrossHairs()
        {
            int crossHairSize = 10;

            if(this.crossHairs == null)
            {
                crossHairs = new Line(m_Device3d);//構造線對象
            }

            Vector2[] vertical = new Vector2[2];
            Vector2[] horizontal = new Vector2[2];
           // Vector2[] test = new Vector2[2];//這是我試驗添加的，效果請看下面的截圖
            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();
        }

上面註銷部分（我加了紅線）是我試驗添加的，效果請看上面的截圖。其實就是劃幾條兩點之間的線。

顯示位置信息

 

 　　是在Render()中調用RenderPositionInfo()方法的，請看該段實現代碼。

實現顯示位置座標信息  


         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;

　　　　　　　　　//構造顯示位置座標信息字符串
                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();

　　        //定義要畫出文本的樣式
            DrawTextFormat dtf = DrawTextFormat.NoClip | DrawTextFormat.WordBreak | DrawTextFormat.Right;
            int x = 7;
            int y = _menuBar!=null && World.Settings.ShowToolbar ? 65 : 7;

　　　　　　　//定義盛放位置文本的矩形框
            Rectangle textRect = Rectangle.FromLTRB(x,y, this.Width-8, this.Height-8 );
            //我添加的測試用代碼
            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處於活動狀態，則更改位置文本的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對象defaultDrawingFont的DrawText（）實現繪製位置信息
            this.drawArgs.defaultDrawingFont.DrawText( null, captionText, textRect, dtf, positionBackColor);
            textRect.Offset(-1,-1);
            this.drawArgs.defaultDrawingFont.DrawText( null, captionText, textRect, dtf, positionForeColor);

//下面這行是我添加的，測試用
            this.drawArgs.defaultDrawingFont.DrawText(null, "無痕客在研究WorldWind應用！", textRect, dtf,Color.Red.ToArgb());
        }

上面需要注意的知識點就是：使用Font對象（實例：defaultDrawingFont）的DrawText（）實現繪製文本信息。

地球軸線繪製

    WorldWindow.cs的Render()方法中調用了World.cs中Render()方法，該方法又調用了DrawAxis（）

方法實現地球軸線繪製。

 

453行 if (Settings.showPlanetAxis)

              this.DrawAxis(drawArgs);

畫地球軸線 




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-->
        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;

        }