I ran into a problem while displaying KML files in Cesium. If the KML file contains "superoverlays" - a multi-resolution image pyramid of groundOverlays, produced e.g. with Global Mapper - rendering will be ugly as Regions and LODs assigned to GroundOverlay elements seem not to take effect.
such a KMZ file is here:
As a temporary solution, I can hide all those Rectangles from KmlDataSource entities, that have bounding boxes that entirely contain other Rectangles from the same source (meaning that they are lower-resolution images)
sample code is here:
After loading, zoom in to see the rendering problem. Press the button in the top left corner to hide lower resolution images causing the problem.
If there is a better solution, please let me know.