Remove Occlusion is a utility that prevents the game from un rendering things it thinks you can't see especially in some instances where things are flickering in between gaps, through a window, or in the distance, 

Although this mod has some issues including the game taking half a second to load and you may notice a drop in FPS in some areas. Hence, to resolve this, you can just edit the files which are typically edited in lighting mods, therefore, making it incompatible with particular lighting mods or anywhere else that allows editing a w2w file. If you prefer making the change yourself, all they need to do is set umbrascene to NULL on whatever the parent tab in the w2w file is.