Ya3dag is based on the quake 2 modification Quake2maX and the lazarus game dll. Want to create your own levels? Well, you've come to the right place. Ya3dag has a built-in "what you see is what you get" level-editor and has been specifically designed for rapid level creation. Terrain, smart NPC's, weather, physic simulation, ...
The underworld exists beneath the terrain. It is intended for dungeons and interiors of buildings. In order to optimize the frame rate, the drawing process for the underworld and the grounds are separated from each other.
This feature will be part of the next release.