Clear buffers for each frustum to fix multifrustum artifact.
Clear buffers for each frustum to fix multifrustum artifact.

josh-bernstein/cesium,geoscan/cesium,progsung/cesium,hodbauer/cesium,NaderCHASER/cesium,YonatanKra/cesium,geoscan/cesium,oterral/cesium,soceur/cesium,kaktus40/cesium,CesiumGS/cesium,YonatanKra/cesium,likangning93/cesium,CesiumGS/cesium,hodbauer/cesium,soceur/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,josh-bernstein/cesium,AnalyticalGraphicsInc/cesium,oterral/cesium,soceur/cesium,hodbauer/cesium,likangning93/cesium,jasonbeverage/cesium,CesiumGS/cesium,YonatanKra/cesium,likangning93/cesium,NaderCHASER/cesium,NaderCHASER/cesium,likangning93/cesium,YonatanKra/cesium,progsung/cesium,kaktus40/cesium,CesiumGS/cesium,oterral/cesium,jasonbeverage/cesium,CesiumGS/cesium