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a4445d521f
Decoded from SKIDMARKS_CD32: - Computer drivers: the path of nodes laid 2 game units apart along the middle of the road, with side points 1 unit in from each wall. Drivers aim four nodes past where they'll be in four frames, or cut to the other side two nodes on at 70% throttle when running wide. Replaces the pure-pursuit AI; laps are quicker on every track. - Collisions: six points on the player's car (corners and sides, from .set words 6 and 7, now known to be half-length and half-width) are tested against the other car's box. Hits push the cars apart with a strength that grows with their speed difference, and spin the car. As in the original, only human players' cars collide; cars at different heights don't. - Towing: the hitch is at the car's back, the caravan sits 0.656 units behind it, and past 90 degrees both car and caravan bend back. The reconstructed collision weight (`mass`) is gone; old asset files with it still load.
Game assets
Everything the game uses is stored here as editable files. The build embeds this folder into the executable. To pick up changes:
- Rebuild:
cargo run --release. - Or skip the rebuild: run with
--data assets. Files given with--dataoverride the built-in copy.
These files were converted from the original Amiga disks with
skids extract --data <folder with the ADFs>. That conversion is lossless,
and running it again overwrites your edits.
Tracks: tracks/<name>/
track.png
The track picture: 1024 × 512, a 16-colour indexed (palette) image.
- Palette: the PNG's palette is the track's palette. Change a palette entry to recolour every pixel that uses it.
- Road vs scenery: colours 8–15 are road; colours 0–7 are scenery, where cars throw up dust. The picture doesn't affect handling. The walls come from the gates (below).
- Painting a new route: paint it with the upper eight colours and update the gates to match.
- Saving: keep the image indexed if your editor allows it. If it saves as full-colour RGB instead, each pixel is matched to the nearest default colour, which loses your palette.
track.txt
Plain text; lines starting with # are comments.
gate x1 y1 x2 y2: lap gates in race order.- Gate 0 is the start/finish line, and the grid forms up behind it.
- Cars must cross every gate, in order, to complete a lap.
- Walls: the gates' ends also shape the road. One edge is a smooth
curve through every gate's first end (
x1 y1), the other through every second end (x2 y2). Those curves are the walls, and computer drivers follow the road between them. The curves pass halfway between neighbouring gates' ends and round off the corners, as in the original. - Coordinates are on the isometric ground plane. To find where a point
on the ground sits in the picture, with
zits height in pixels (fromheight):picture x = wx - wy + 512,picture y = (wx + wy) / 2 − 156 − z. skids trace --data assets --track N --out t.pngdraws the walls (grey), the gates (gate 0 in yellow) and the computer cars' paths over the picture.
height: 64 rows of 64 numbers giving ground height in pixels × 64.- Layout: the rows run along world y and the numbers within a row along world x. Each covers 16 × 16 world units.
- Effect: climbing slows cars and descending speeds them up. Cars leave the ground over crests that drop away faster than gravity, and the car sprites tilt with the slope.
set: the name of the set of tracks this one belongs to, shown under the menu thumbnail.start,flags: values from the original data that the game doesn't use.
thumb.png (optional)
The track's 123 × 32 thumbnail from the original track-select screen, in
the track's palette. It's drawn at double height in the menu, because the
original's pixels are half-width. Without one, the menu shows a shrunken
track.png.
To add a track, make a new folder with track.png and track.txt. Tracks are listed in
name order.
Vehicles: vehicles/<id>.png and <id>.txt
<id>.png
A 2048 × 800 sprite sheet: 32 headings across by 25 tilts down, each cell 64 × 32.
-
Colours: use only palette indices 0–3:
- 0 transparent
- 1 tyres / shadow
- 2 trim
- 3 bodywork
The colours in the file are only a preview; each player's car is recoloured at run time.
-
Headings: column 12 faces right, and columns advance clockwise in 11.25° steps.
-
Tilts: row = roll × 5 + pitch (each 0–4), so row 12 is the car on flat ground.
<id>-menu.png (optional)
The car's 64 × 32 picture from the original select screen, in the same four colours as the sprite sheet.
<id>.txt
The display name, driver and handling:
| Setting | Meaning |
|---|---|
name |
name shown in the menu |
driver |
driver's name, shown next to it |
trailer |
yes for something towed behind cars (the caravan) rather than driven |
handling |
the 16 values from the original .set file, used as the original game uses them (below) |
The handling values, counting from 1:
| Value | Meaning |
|---|---|
| 1, 2, 6 | computer drivers: drag, grip, power |
| 9, 10, 11 | human drivers: drag, grip, power |
| 3 | steering: 16 = 1/64 of a turn per frame at full lock |
| 5 | gravity: 8 = 1 pixel per frame² |
| 7, 8 | half the car's length and width, for collisions: 2 = 1 world unit. The tow hitch is at the back. |
| 4, 12–16 | unused |
What the driving values do:
- Drag (below 64): how much of the engine's speed survives each frame. Low drag gives fast pick-up and fast slowing.
- Power: what the throttle adds.
- Top speed:
power × drag / (64 − drag) / 32world units per frame, at 50 frames a second. - Grip: how quickly the car's movement turns to follow where it's pointing. Low grip means long slides.
The menu's Handling option can replace every car's values with one of the original's presets.
Older files with original, top, accel, brake, grip, turn,
offroad and mass lines still load: original is read as handling,
and the others are ignored. To add a car, add a new <id>.png / <id>.txt pair.
Sounds: sounds/*.wav
8-bit mono WAV files at the original Amiga sample rates. A loop point,
stored in the WAV's smpl chunk, makes a sound repeat from there; most
sample editors keep it. The game uses these names:
| Sound | Use |
|---|---|
motor3 |
engine, pitched up and down with revs (falls back to motor, then engine) |
screech2 |
tyres sliding (falls back to screech3, then screech) |
crash1, crash2, crash3 |
collisions, picked at random |
backfire |
lifting off at high revs |
horn |
Right Shift (player 1) or Left Shift (player 2) |
beep, beep2 |
countdown, then lights out |
Missing sounds fall back to synthesised ones. Any other WAV files are kept but not used.
Music: music/*.med
The tune, an OctaMED module. Edit it in a tracker that reads MED files,
such as OpenMPT. The game's player supports plain sample instruments (no
synth sounds) and the commands listed in docs/FORMATS.md. Preview it
with skids music --data assets --out tune.wav. If there are several
files, the first in name order plays.
Pictures: gfx/*.png
Indexed PNGs. skidtoon.png is the title picture at the top of the menu,
shown at half size. The others aren't used:
ball.png: 64 frames of a spinning ball with the Acid logo, 16 frames across, each 32 × 33. Its real colours aren't known, so it has a grey palette.chat2.png,mouse.png,sign.png: small odds and ends.
Palettes: palettes/*.pal (optional)
16 lines of RRGGBB. Each file overrides the PNG palettes:
track1-3.pal: one tracktrack1.pal: every TRACK1 trackdefault.pal: all tracks