The Drag[en]gine is a fully customizable game engine and game development environment designed with modularity and extensibility in mind not requiring expensive licenses.
Visualization of some visibility meshes. They are created by the mapper and are very simplistic. Their purpose is to determine visible space. They are of low polygon count and quickly created. For example a complex room system only needs some boxes around the rooms no matter how elaborated the room itself is. Nobody else than the mapper knows best the logic of his map.