function AutoExposure() {
  this._uniformMap = undefined;
  this._command = undefined;

  this._colorTexture = undefined;
  this._depthTexture = undefined;

  this._ready = false;

  this._name = "czm_autoexposure";

  this._logDepthChanged = undefined;
  this._useLogDepth = undefined;

  this._framebuffers = undefined;
  this._previousLuminance = new FramebufferManager();

  this._commands = undefined;
  this._clearCommand = undefined;

  this._minMaxLuminance = new Cartesian2();

  /**
   * Whether or not to execute this post-process stage when ready.
   *
   * @type {boolean}
   */
  this.enabled = true;
  this._enabled = true;

  /**
   * The minimum value used to clamp the luminance.
   *
   * @type {number}
   * @default 0.1
   */
  this.minimumLuminance = 0.1;

  /**
   * The maximum value used to clamp the luminance.
   *
   * @type {number}
   * @default 10.0
   */
  this.maximumLuminance = 10.0;
}
A post process stage that will get the luminance value at each pixel and
uses parallel reduction to compute the average luminance in a 1x1 texture.
This texture can be used as input for tone mapping.

@constructor
@private