An alephone plugin that can be used to help you determine if your map has enough differential shading. It will turn all of the floors, ceilings, and walls solid green. If you do not have enough differential shading, it will be difficult or impossible to look around and see the architecture of your map.
If after turning this plugin on, you can navigate your level easily and see all of the architecture, your map has adequate differential shading.
You will likely need to disable other texture plugins and any others that run lua like visual mode when using this plugin.