Fix silhouette post process doc
Fix silhouette post process doc

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