code: function registerDefaultRenderers(stage) {
    switch (stage.type) {
      case 'webgl':
        stage.registerRenderer('flat', 'flat', WebGlFlat);
        stage.registerRenderer('cube', 'rectilinear', WebGlCube);
        stage.registerRenderer('equirect', 'rectilinear', WebGlEquirect);
        break;
      case 'css':
        stage.registerRenderer('flat', 'flat', CssFlat);
        stage.registerRenderer('cube', 'rectilinear', CssCube);
        break;
      case 'flash':
        stage.registerRenderer('flat', 'flat', FlashFlat);
        stage.registerRenderer('cube', 'rectilinear', FlashCube);
        break;
      default:
        throw new Error('Unknown stage type: ' + stage.type);
    }
  }
docs: Registers all known renderers for the given stage type into that stage.
  Most users will not need to register renderers, as {@link Viewer} does it for
  them.
  
  @param {Stage} stage The stage where the renderers are to be registered.
  @throws An error if the stage type is unknown.