Hi,I want to know how to calcuate the precise rectangle in current view,the method computeViewRectangle of Camera only computes the approximate visible rectangle on the ellipsoid. the result always display (-180°,-90°,180°,90°) when I use this method at the level1 and the level2

var rect =;

var northeast = Cesium.Rectangle.northeast(rect);

var northwest = Cesium.Rectangle.northwest(rect);

var southwest = Cesium.Rectangle.southwest(rect);

var southeast = Cesium.Rectangle.southeast(rect);

              Level2                                                           Level1