Assume you have a room with floor-to-ceiling glass window/sliders that are such where you can see people walking by and they can see in. Privacy can be a serious issue. Drapes are a poor solution for obvious reasons. One-way glass works great and one-way films work pretty good during the day but because of their physics they reverse at night so that one cannot see out while those outside can see in. Smart glass which changes from clear to opaque at the flip of an electric switch is a decent solution but it costs tens of thousands of dollars and cannot be split on one pane. Fortunately, all is not lost because there is a reasonable-cost terrific solution: Top-Down/Bottom-Up shades. With them, you can leave the bottom half closed on the bottom half of the glass as the default but open or close them entirely when wanted. And they can be motorized and done by remote and set on a timer. The HD link below explains them more fully.
Hunter Douglas Link: http://www.hunterdouglas.com/product-option.jsp?id=36