Only use new approach if there's more than one frustum
Only use new approach if there's more than one frustum

CesiumGS/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,likangning93/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,likangning93/cesium,CesiumGS/cesium,YonatanKra/cesium,progsung/cesium,YonatanKra/cesium,CesiumGS/cesium,progsung/cesium,likangning93/cesium,YonatanKra/cesium,YonatanKra/cesium