The racing line in TOCA Race Driver

Codemasters' TOCA Race Driver stores AI racing lines in 512 KiB files containing 32,768 16-byte records, with about 21% of each file holding racing-line points and 0.5% control tags that select speed and braking targets, according to a developer's reverse-engineering of the game's binary format. The analysis of 1,371 archives found the data section base varies from 0x60 to 0x5000, not always at 0x800, which caused misreads in about 290 files. The findings are implemented in the open-source Ruby reader lib/bigf/toca/profile.rb.

People who played TOCA Race Driver remember the other cars. They take a line. They brake late and run wide. The compliment is always that they feel driven. I already had the container. Codemasters packed the AI into a BIGF archive: four bytes of magic, a directory, then the files. That is Reading a Binary Game Format in Ruby /2026/06/30/reading-binary-in-ruby.html . This is what those files hold. TOCA Race Driver 1 names 39 AI profiles inside aib.big . A full one is exactly 512 KiB. 32,768 records of 16 bytes, each four little-endian floats. I classified every record by its bit pattern. | record kind | share of file | what it is | |---|---|---| padding 0x3f3f3f3f , the float 0.747 | ~65% | unused fill in a fixed-size slot | racing-line point x0, y0, x1, y1 | ~21% | the line the AI follows | bound scalar v, 0, v, 0 | ~3% | the authored value for a channel | control tag 0c..08 plus a float K | ~0.5% | selects the channel | The points chain. Consecutive x, y pairs sit about fifteen world-units apart on one DTM block the mean gap is 14.4, range 2 to 57 . Plot them and a circuit appears: a start-finish straight, a technical infield. A full profile carries somewhere between 5,000 and 17,000 usable points, depending on the series. The control layer is smaller. A tag 0c 00 00 00 08 00 00 00 plus a float K , then a scalar v, 0, v, 0 immediately after. In one DTM profile there are nine distinct K values. Each shows up about thirty-five times, once per sector. | K | paired v | what it is doing | |---|---|---| | 137 | ≈ 8.0 | speed target | | 552 | ≈ 152 | high target, DTM only | | -135 | ≈ -79.5 | lateral / braking | The authored number sits in the scalar that follows the tag. Follow this line. At this sector, aim for this value. Driver files sitting next to the archive name the other scalars: Aggression, Mistakes, Control, SpeedIn, SpeedOut. They are more tables, loaded once before the grid. I assumed the data section always started at 0x800 . It does in a lot of files. Measuring 1,371 archives showed the base lives in a header field and runs from 0x60 to 0x5000 . The assumption silently misread about 290 files. 32 of the 39 names in RD1’s aib.big are empty stubs. The 512 KiB blobs live in the series archives ela.big , dtm.big using the same layout. .aid , then tiny per-class overlays .aib , 76 to 84 bytes and per-class arrays .red . The 16-byte record vocabulary is the same. An RD2 overlay decodes with the RD1 classifier. 56 modular archives. AILD .Harder profiles are different tables. A different line. Different target values. A wider or narrower error band. Own discs. No game bytes reproduced here, only sizes, magics, and record shapes. The shares in the first table are from a full RD1 profile. Other series spend more or less of the 512 KiB on path against pad. I have not located the per-frame steering function in the executable. Several strings that look like an AI servo belong to force-feedback and the TV camera. I am leaving those out until a later pass. The classifier is in the same public reader as the container: lib/bigf/toca/profile.rb