Dark Engine

The Dark Engine's renderer, originally created by Sean Barrett in 1995, supports graphics similar to that of the original Quake, with Unreal-like skybox effects and colored lighting introduced in Thief 2. Due to the limited hardware of the time, the Dark Engine was not designed with scalability in mind, and can therefore only display 1024 terrain polygons onscreen at once, as well as various other limits on objects and lights. In terms of textures, the game supports palletized PCX and TGA textures, in powers of two up to 256x256. Textures are grouped in "families" which share the same palette. There is a maximum of 216 textures and independent palettes, excluding 8 animated water textures.

The engine does not natively support advanced game scripting, with AI and object behavior being controlled by 'Object Script Module' (.OSM) files, which are DLLs which are loaded at runtime. As such, new modules can be written and plugged into the level editor, DromEd, but are limited due to the scope of the functions made available by the core engine. In order to overcome this, editors must resort to complicated Rube Goldberg machine-like effects using a combination of its other systems.

For its time, the Dark Engine offers advanced AI and sound features, as well as a powerful object-oriented object system. The designer has full control of sound propagation within the level, and the "artificial intelligence" of the non-player characters (NPCs) allows for three levels of awareness: vague acknowledgement caused by mild visual or auditive disturbances, which only prompts a startled bit of dialogue; definite acknowledgement caused by significant visual or auditive disturbances which causes the NPC to enter "search mode", and definite acquisition (triggered by visual on the fully lit player, or face-first contact with a player regardless of the light level), prompting a direct attack.