The X-ray Engine is a DirectX 8.1/9 Shader Model 3.0 graphics engine. Up to a million polygons can be on-screen at any one time. The engine features HDR rendering, parallax and normal mapping, soft shadows, motion blur, widescreen support, weather effects and day/night cycles. As with other engines that utilise deferred shading, the X-ray Engine does not support anti-aliasing with dynamic lighting enabled. However, a "fake" form of anti-aliasing can be enabled with the static lighting option; this format utilizes a technique to blur the image to give the false impression of anti-aliasing. The game takes place in a thirty square kilometer area, and both the outside and inside of this area is rendered to the same amount of detail. Some textures in the game were simply photographs of the walls in the developers' studio.
Awesome engine for an awesome game! :)
It can handle a lot of npcs and big areas, supports 'special thigs' (anomalies in STALKER) and the optimization is great too. You can actually play the games with an 8 years old computer (2013), but (with better textures) you can make the looking almost fully realistic!