maximumCacheOverflowBytes
The maximum additional amount of GPU memory (in bytes) that will be used to cache tiles.
If tiles sized more than cacheBytes plus maximumCacheOverflowBytes are needed to meet the desired screen space error, determined by Cesium3DTileset.maximumScreenSpaceError for the current view, then Cesium3DTileset.memoryAdjustedScreenSpaceError will be adjusted until the tiles required to meet the adjusted screen space error use less than cacheBytes plus maximumCacheOverflowBytes.