This help page describes the basic concepts involved in the structure of a NFS3 track. For technical information on the NFS3 file formats, please refer to the page on NFS3 Track File Formats.
Track structure
NFS3 tracks are subdivided into track blocks (ca. 200-300 of them), each of which consists of track vertices, polygons, objects and virtual road data. The corresponding data are mostly stored in a file with extension .FRD, and also in a companion file with .COL extension.
Vertices
These are the points which make up the track. They can belong either to the main track structure, or to an "extra object" (see below).
Polygons
A track block consists of three series of polygons, corresponding to various resolutions (the low and medium resolutions are only used to save computing time when the car is still far away). To every polygon corresponds a texture, and the high-resolution series of polygons is also associated with virtual road information.
Objects
There are two types of objects : the polygon objects (displayed in blue in T3ED) make use of the same list of vertices as the main track structure, while the extra objects (displayed in green in T3ED) have separate vertex information structures. The polygon objects are fixed and cannot be collided with, while the extra objects feature collision detection and can be animated as well.
Virtual Road
The virtual road is all the information used by NFS3 in order to compute the behavior of the various cars (player, police, opponents or traffic). This includes, in particular, a sequence of "virtual nodes" stored in the associated .COL file ; virtual forward and normal vectors associated to every high resolution track polygon ; etc...
Textures
The track textures are stored in a companion file with .QFS extension. Four files are provided for each track : the files whose names end with a ‘0‚ correspond to normal racing, while those which contain a ‘1‚ correspond to mirrored tracks. The files with a ‘_8‚ suffix in their name correspond to 256-color textures, while the others correspond to 65536-color textures.