function underground(t, i) {
            this._viewer = t;
            var n = Cesium.defaultValue(i, {});
            this._depth = Cesium.defaultValue(n.depth, 500),
                this._alpha = Cesium.defaultValue(n.alpha, .5),
                this.enable = Cesium.defaultValue(n.enable, !1)
        }
        underground.prototype._updateImageryLayersAlpha=function(e) {
            for (var t = this._viewer.imageryLayers._layers, i = 0, a = t.length; i < a; i++)
                t[i].alpha = e
        }
        underground.prototype._historyOpts =function() {
            var e = {};
            e.alpha = Cesium.clone(this._viewer.imageryLayers._layers[0] && this._viewer.imageryLayers._layers[0].alpha),
                e.highDynamicRange = Cesium.clone(this._viewer.scene.highDynamicRange),
                e.skyShow = Cesium.clone(this._viewer.scene.skyAtmosphere.show),
                e.skyBoxShow = Cesium.clone(this._viewer.scene.skyBox.show),
                e.depthTest = Cesium.clone(this._viewer.scene.globe.depthTestAgainstTerrain),
            this._viewer.scene.globe._surface && this._viewer.scene.globe._surface._tileProvider && this._viewer.scene.globe._surface._tileProvider._renderState && (e.blending = Cesium.clone(this._viewer.scene.globe._surface._tileProvider._renderState.blending)),
                this._oldViewOpts = e
        }
        underground.prototype.activate =function() {
            if (!this._enable) {
                this._enable = !0,
                    this._historyOpts(),
                    this._updateImageryLayersAlpha(this._alpha);
                var e = this._viewer;
                Cesium.ExpandByMars.underEarth.cullFace = !1,
                    Cesium.ExpandByMars.underEarth.enable = !0,
                    Cesium.ExpandByMars.underEarth.enableDepth = this._depth,
                    Cesium.ExpandByMars.underEarth.enableSkirt = !0,
                    e.scene.globe.depthTestAgainstTerrain = !0,
                    e.scene.highDynamicRange = !1,
                    e.scene.skyAtmosphere.show = !1,
                    e.scene.skyBox.show = !1,
                e.scene.globe._surface._tileProvider && e.scene.globe._surface._tileProvider._renderState && e.scene.globe._surface._tileProvider._renderState.blending /*&& (e.scene.globe._surface._tileProvider._renderState.blending.enabled = !0,
        e.scene.globe._surface._tileProvider._renderState.blending.equationRgb = Cesium.BlendEquation.ADD,
        e.scene.globe._surface._tileProvider._renderState.blending.equationAlpha = Cesium.BlendEquation.ADD,
        e.scene.globe._surface._tileProvider._renderState.blending.functionSourceAlpha = Cesium.BlendFunction.ONE,
        e.scene.globe._surface._tileProvider._renderState.blending.functionSourceRgb = Cesium.BlendFunction.ONE,
        e.scene.globe._surface._tileProvider._renderState.blending.functionDestinationAlpha = Cesium.BlendFunction.ZERO,
        e.scene.globe._surface._tileProvider._renderState.blending.functionDestinationRgb = Cesium.BlendFunction.ZERO)*/
            }
        }
        underground.prototype.disable=function() {
            if (this._enable) {
                this._enable = !1,
                    this._updateImageryLayersAlpha(this._oldViewOpts.alpha);
                var e = this._viewer;
                Cesium.ExpandByMars.underEarth.cullFace = void 0,
                    Cesium.ExpandByMars.underEarth.enable = !1,
                    Cesium.ExpandByMars.underEarth.enableDepth = 0,
                    Cesium.ExpandByMars.underEarth.enableSkirt = !1,
                    e.scene.globe.depthTestAgainstTerrain = this._oldViewOpts.depthTest,
                    e.scene.skyBox.show = this._oldViewOpts.skyBoxShow,
                    e.scene.highDynamicRange = this._oldViewOpts.highDynamicRange,
                    e.scene.skyAtmosphere.show = this._oldViewOpts.skyShow/*,
        void 0 != this._oldViewOpts.blending && (e.scene.globe._surface._tileProvider._renderState.blending = this._oldViewOpts.blending)*/
            }
        }
        underground.prototype.destroy=function(){
           delete this._viewer,
           delete this._alpha,
           delete this._depth,
           delete this._enable,
           delete this._oldViewOpts
        }