Base layer stretch

Hi All,

Regarding to an old thread in 2014 below:!searchin/cesium-dev/regional$20data/cesium-dev/3SSScyR_d1I/qpgXeAFR3ssJ

I have exactly the same problem, which I am trying to display regional data with base layer, and the base layer is stretched. I am wondering is there an option to turn off the automatically base layer stretch?