1 相机的初始位置

/**
 * The default rectangle the camera will view on creation.
 * @type Rectangle
 */
Camera.DEFAULT_VIEW_RECTANGLE = Rectangle.fromDegrees(
  -95.0,
  -20.0,
  -70.0,
  90.0
);

// set default view
rectangleCameraPosition3D(
  this,
  Camera.DEFAULT_VIEW_RECTANGLE,
  this.position,
  true

2 相关矩阵

// 视图矩阵
_viewMatrix

3 类结构

Camera
  ┣ OrthographicFrustum(frustum)
  ┃   ┖ OrthographicOffCenterFrustum(_offCenterFrustum)
  ┃
  ┖ PerspectiveFrustum(frustum)
      ┖ PerspectiveOffCenterFrustum(_offCenterFrustum)

PerspectiveFrustum 把 PerspectiveOffCenterFrustum 进行了包装, 内部实际上是调用了 PerspectiveOffCenterFrustum 。

4 创建过程

// PerspectiveFrustum 的创建
class Camera {
  constrouctor() {
    this.frustum = new PerspectiveFrustum();
    this.frustum.fov = CesiumMath.toRadians(60.0);
  }
}

// PerspectiveOffCenterFrustum 的创建
class PerspectiveFrustum {
  constrouctor() {
    this._offCenterFrustum = new PerspectiveOffCenterFrustum();
  }
}

5 更新和赋值

PerspectiveFrustum 更新时机例子:

// Camera.js
Camera.constrouctor()
  fn rectangleCameraPosition3D()
    // PerspectiveFrustum.js
    get camera.frustum.fovy()
      fn update();
        // 1) 为 PerspectiveFrustum 赋值
        // 2) 为 PerspectiveOffCenterFrustum 赋值

PerspectiveOffCenterFrustum 更新时机例子:

// Scene.js
fn render()
  context.uniformState.update()
    // UniformState.js
    this.updateCamera()
      this.updateFrustum()
        // PerspectiveOffCenterFrustum.js
        get projectionMatrix()
          fn update()