Trackdata

Trackdata is a set of twenty three data structures which hold key information about the track in use and the lap being driven or replayed on it. Each of the individual data structures is referred to as trackdataXX, with XX being a two-digit number. The current systematisation of Trackdata is chiefly based on the results of the restunts project, though parts of it have been independently discovered and rediscovered over the years.

Finding Trackdata in memory

The most convenient targets to look for when using a debugger to locate Trackdata in memory are trackdata11 (highscore table), trackdata13 (replay file header) and trackdata14 (element map as in the track file). Keep in mind that different parts of Trackdata might be loaded or not depending on the current game phase (pre-lap, playing, replaying, or post-lap).

Trackdata data structures

Offsets and byte sizes assume the 1991 DOS versions of Stunts.

#	Offset (hex)	Size (hex)	Size	Layout	Description	Notes
01	0	70a	1802	901 words	Track continuity: each value is the index of the next element in driving order. Alternative dual-way paths show up after the main one.	The 901-value sizes of the driving-order structures is reflected by the "too many track pieces" validation error.
02	70a	70a	1802	901 words	Split points: for dual-way splits, the value is the index of the first element of the alternative path, in driving order.
03	e14	70a	1802	901 words	Opponent path: sequence of elements to be driven by the opponent. Starts from 0x0, the start/finish line.	Occasionally changes upon restarting a race or reloading a replay.
04	151e	80	128	64 words	Player aero table: aerodynamic resistance lookup table. Indexed by speed_mph >> 2.
05	159e	80	128	64 words	Opponent aero table: aerodynamic resistance lookup table. Indexed by speed_mph >> 2.
06	161e	80	128
07	169e	80	128	64 words
08	171e	60	96	48 words?
09	18fe	180	384	64 3D word vectors	F4 camera positions. Absolute coordinates, graphical units.
10	1a1e	120	288	48 3D word vectors	Corner sign positions. Absolute coordinates, graphical units.
11	1b8a	16c	364	Highscore File Format	Highscore table.
12	1c7a	f0	240
13	1c9a	1a	26	Replay File Format	Replay header.
14	2019	385	901	Track File Format	Track file element map, plus the scenery byte	Appears to control only the graphical rendering, and not the physical model.
15	239e	385	901	Track File Format	Track file terrain map, plus the padding byte
16	527e	2ee0	12000	Replay File Format	Replay input buffer.	This is the safe memory area used by Bliss track metadata.
17	5603	385	901	901 bytes	Track elements, in driving order
18	5988	385	901	901 bytes		Likely related to element connectivity checks. The values appear to be structured as bit flags.
19	5d0d	385	901	Track file-like map	Indices for trackdata10 (corner signs).
20	64b9	7ac	1964			The first 1802 bytes are a copy of the track file.
21	683e	385	901	901 bytes	Grid column of track elements, in driving order
22	6bc3	385	901	901 bytes	Grid row of track elements, in driving order
23	6bf3	30	48	48 bytes?