CSharpGL(4)设计和使用Camera
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描述在OpenGL中Camera的概念和用处。
设计一个Camera以及操控Camera的SatelliteRotator。
以PyramidElement为例演示如何使用Camera和SatelliteRotator。
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下载
您可以在（https://github.com/bitzhuwei/CSharpGL）找到最新的源码。欢迎感兴趣的同学fork之。
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Camera
在OpenGL中的Camera概念可以方便我们设定projection矩阵和view矩阵。
定义
1 /// <summary> 2 /// 摄像机。 3 /// </summary> 4 public class Camera : 5 ICamera, 6 IPerspectiveViewCamera, IOrthoViewCamera, 7 IViewCamera, IPerspectiveCamera, IOrthoCamera 8 { 9 /// <summary> 10 /// 默认目标为vec3(0, 0, 0) 11 /// </summary> 12 public static readonly vec3 defaultTarget = new vec3(0, 0, 0); 13 14 /// <summary> 15 /// 默认位置为vec3(0, 0, 1) 16 /// </summary> 17 public static readonly vec3 defaultPosition = new vec3(0, 0, 1); 18 19 /// <summary> 20 /// 默认上方为vec3(0, 1, 0) 21 /// </summary> 22 public static readonly vec3 defaultUpVector = new vec3(0, 1, 0); 23 24 internal Camera() { } 25 26 /// <summary> 27 /// 摄像机。 28 /// </summary> 29 /// <param name="cameraType">类型</param> 30 /// <param name="width">OpenGL窗口的宽度</param> 31 /// <param name="height">OpenGL窗口的高度</param> 32 public Camera(CameraType cameraType, double width, double height) 33 { 34 this.lastHeight = width; 35 this.lastHeight = height; 36 37 IPerspectiveCamera perspectiveCamera = this; 38 perspectiveCamera.FieldOfView = 60.0f; 39 perspectiveCamera.AspectRatio = width / height; 40 perspectiveCamera.Near = 0.01; 41 perspectiveCamera.Far = 10000; 42 43 const int factor = 100; 44 IOrthoCamera orthoCamera = this; 45 orthoCamera.Left = -width / 2 / factor; 46 orthoCamera.Right = width / 2 / factor; 47 orthoCamera.Bottom = -height / 2 / factor; 48 orthoCamera.Top = height / 2 / factor; 49 orthoCamera.Near = -10000; 50 orthoCamera.Far = 10000; 51 52 this.Target = defaultTarget; 53 this.Position = defaultPosition; 54 this.UpVector = defaultUpVector; 55 56 this.CameraType = cameraType; 57 } 58 59 public void Resize(double width, double height) 60 { 61 double aspectRatio = width / height; 62 63 IPerspectiveCamera perspectiveCamera = this; 64 perspectiveCamera.AspectRatio = aspectRatio; 65 66 IOrthoCamera orthoCamera = this; 67 68 double lastAspectRatio = this.lastWidth / this.lastHeight; 69 if (aspectRatio > lastAspectRatio) 70 { 71 double top = orthoCamera.Top; 72 double newRight = top * aspectRatio; 73 orthoCamera.Left = -newRight; 74 orthoCamera.Right = newRight; 75 } 76 else if (aspectRatio < lastAspectRatio) 77 { 78 double right = orthoCamera.Right; 79 double newTop = right / aspectRatio; 80 orthoCamera.Bottom = -newTop; 81 orthoCamera.Top = newTop; 82 } 83 84 //const int factor = 100; 85 //if (width / 2 / factor != orthoCamera.Right) 86 //{ 87 // orthoCamera.Left = -width / 2 / factor; 88 // orthoCamera.Right = width / 2 / factor; 89 //} 90 //if (height / 2 / factor != orthoCamera.Top) 91 //{ 92 // orthoCamera.Bottom = -height / 2 / factor; 93 // orthoCamera.Top = height / 2 / factor; 94 //} 95 } 96 97 double lastWidth; 98 double lastHeight; 99 100 /// <summary> 101 /// Gets or sets the target. 102 /// </summary> 103 /// <value> 104 /// The target. 105 /// </value> 106 [Description("The target of the camera (the point it's looking at)"), Category("Camera")] 107 public vec3 Target { get; set; } 108 109 /// <summary> 110 /// Gets or sets up vector. 111 /// </summary> 112 /// <value> 113 /// Up vector. 114 /// </value> 115 [Description("The up direction, relative to camera. (Controls tilt)."), Category("Camera")] 116 public vec3 UpVector { get; set; } 117 118 /// <summary> 119 /// The camera position. 120 /// </summary> 121 private vec3 position = new vec3(0, 0, 0); 122 123 /// <summary> 124 /// Every time a camera is used to project, the projection matrix calculated 125 /// and stored here. 126 /// </summary> 127 private mat4 projectionMatrix = mat4.identity(); 128 129 ///// <summary> 130 ///// The screen aspect ratio. 131 ///// </summary> 132 //private double aspectRatio = 1.0f; 133 134 /// <summary> 135 /// Gets or sets the position. 136 /// </summary> 137 /// <value> 138 /// The position. 139 /// </value> 140 [Description("The position of the camera"), Category("Camera")] 141 public vec3 Position 142 { 143 get { return position; } 144 set { position = value; } 145 } 146 147 /// <summary> 148 /// camera's perspective type. 149 /// </summary> 150 public CameraType CameraType { get; set; } 151 152 #region IPerspectiveCamera 成员 153 154 double IPerspectiveCamera.FieldOfView { get; set; } 155 156 double IPerspectiveCamera.AspectRatio { get; set; } 157 158 double IPerspectiveCamera.Near { get; set; } 159 160 double IPerspectiveCamera.Far { get; set; } 161 162 #endregion 163 164 #region IOrthoCamera 成员 165 166 double IOrthoCamera.Left { get; set; } 167 168 double IOrthoCamera.Right { get; set; } 169 170 double IOrthoCamera.Bottom { get; set; } 171 172 double IOrthoCamera.Top { get; set; } 173 174 double IOrthoCamera.Near { get; set; } 175 176 double IOrthoCamera.Far { get; set; } 177 178 #endregion 179 }