Only copy vertices that can't be shared.
Only copy vertices that can't be shared.

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