The graphic technology of the game is based tightly around a "shader" system where the appearance of many surfaces can be defined in text files referred to as "shader scripts". "Quake 3" also introduced spline-based curved surfaces in addition to planar volumes, which are responsible for many of the surfaces present within the game. "Quake 3" also provided support for models animated using vertex animation with attachment tags (known as the .md3 format), allowing models to maintain separate torso and leg animations and hold weapons. "Quake 3" is one of the first games where the third-person model is able to look up and down and around as the head, torso and legs are separate. Other visual features include volumetric fog, mirrors, portals, decals, and wave-form vertex distortion.