Add the contents of disk 1
- LHA -lh5/-lh6/-lh7 decoding with CRC checks (disk 1 is mostly lh5) - Real track palettes and set names, read from each track file's header - Camaro, plus the caravan as a towable trailer (Caravans option) - Drivers' names, menu pictures and the original .set values per car - Original sound effects (IFF 8SVX) through a new sample mixer: engine pitched with revs, tyre screech, crashes, backfire, horn, start beeps - The original tune (OctaMED MMD1) through a new player; loudness tracks OpenMPT's render through the whole song. Music option in the menu - Title picture (IFF ILBM) at the top of the menu - skids unpack and skids music commands - Gate crossings now judged on each car's whole movement per frame, including collision knocks; stalled computer cars are put back on the line after 8 seconds The executable's game logic (handling, AI) is still not decoded.
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# Super Skidmarks data formats
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Notes from reverse engineering the AGA/CD32 release of *Super Skidmarks*
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(Acid Software, 1995). Everything here was worked out from the data on disks
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2–6. Disk 1, which holds the executable, is missing from this archive, so
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anything that lives only in the executable (palettes, sound, handling) is
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unknown. See [Gaps](#gaps).
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(Acid Software, 1995), worked out from all six disks. The one thing not
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yet decoded is the executable's game logic. See [Gaps](#gaps).
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All multi-byte values are big-endian unless noted.
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## Disks
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Each disk is a standard 880 KB double-density ADF (1760 blocks of 512 bytes)
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formatted as OFS (`DOS\0`). The `[HD]` in the file names refers to the
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hard-drive-installable release, not high-density disks. Each disk holds a
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single file:
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Each disk is a standard 880 KB double-density ADF (1760 blocks of 512
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bytes). Disk 1 is FFS (`DOS\1`); disks 2–6 are OFS (`DOS\0`). The `[HD]` in
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the file names refers to the hard-drive-installable release.
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| Disk | File | Contents |
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|------|---------------|------------------------------------|
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| 1 | `smcd32a.lha` | *missing* |
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| Disk | Archive | Game files |
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|------|---------------|------------|
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| 1 | `smcd32a.lha` | Executables, `sfx/`, `gfx/`, the tune, `vehicles/*.set`, `Camaro.aga`, `caravan.aga` |
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| 2 | `smcd32b.lha` | `vehicles/cow.aga`, `track/TRACK1` |
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| 3 | `smcd32c.lha` | `track/TRACK2`, `vehicles/TRUCK.aga` |
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| 4 | `smcd32d.lha` | `track/TRACK3`, `vehicles/PORSCHE.aga` |
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| 5 | `smcd32e.lha` | `track/track4`, `vehicles/vw.aga` |
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| 5 | `smcd32e.lha` | `track/track4`, `vehicles/vw.aga` |
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| 6 | `smcd32f.lha` | `vehicles/F1.aga`, `Midget.aga`, `mini.aga`, `Police.aga` |
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Each disk's archive stands on its own (the set isn't one archive split
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across disks). They use level-0 headers and the `-lh0-` method (stored),
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under a top-level `super_skidmarks_cd³²\` directory. Most members are
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individually packed with CrunchMania.
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Disk 1 also carries an Installer script that installs from all six disks,
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and a few AmigaDOS commands.
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Each archive stands on its own; the set isn't one archive split across
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disks. They use level-0 headers under a top-level `super_skidmarks_cd³²\`
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directory.
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- **Compression:** disks 2–6 store their members (`-lh0-`), which are
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themselves CrunchMania-packed. Disk 1 mostly uses `-lh5-` (LZSS with
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static Huffman blocks, decoded by `src/formats/lzh.rs`).
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- **Integrity:** every member is checked against its header CRC-16. One
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file, `c/iconx` (an AmigaDOS utility the game doesn't use), fails its CRC
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in this dump. The reference `lha` tool reports the same failure.
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## CrunchMania
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@@ -52,12 +58,25 @@ consumed to its first byte.
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```
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0x00 7 × u32 end offset of sections 0..6
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0x1C … section 0: track-selector thumbnails (20622 bytes, raw)
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0x1C … section 0: header for the whole file (20622 bytes, raw)
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… sections 1..6: one track each, CrunchMania-packed
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```
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So the four files hold 24 tracks. Each track section unpacks to 281240
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(`0x44A98`) bytes:
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So the four files hold 24 tracks.
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The last 142 bytes of section 0 hold:
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| Offset | Size | Contents |
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|--------|------|----------|
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| 0 | 2 | File number (1–4) |
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| 2 | 96 | The palette shared by the file's six tracks: 16 colours × R, G, B, each a `u16` from 0 to 15 (Amiga 12-bit colour) |
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| 98 | 12 | Unknown |
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| 110 | … | The name of the set of tracks, NUL-terminated |
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The rest of section 0 is the track-selector thumbnails, which aren't
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decoded.
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Each track section unpacks to 281240 (`0x44A98`) bytes:
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| Offset | Size | Contents |
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|----------|--------|----------|
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@@ -88,14 +107,15 @@ The stored start point is on the road for 14 of the 24 tracks read as screen
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coordinates, and 10 read as world coordinates. It isn't used; the grid forms
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up behind gate 0.
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### Palette use
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### Road and scenery
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The track pixel indices are ordered from dark to light. Indices 0–7 are
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scenery and 8–15 the driving surface, so the fourth bitplane is effectively
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a road mask. The game uses it as such here: off-road means less grip and
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Colours 8–15 are the driving surface on every track, so the fourth
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bitplane is effectively a road mask. Off the road means less grip and
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lower speed.
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## Vehicles (`vehicles/*.aga`)
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## Vehicles
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### Sprite banks (`vehicles/*.aga`)
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CrunchMania-packed, 409600 bytes unpacked:
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25 tilt blocks × 32 headings × 512-byte frames.
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@@ -112,27 +132,78 @@ A frame is a 64 × 32 AGA hardware sprite. Each line holds 8 bytes of plane
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- **Heading:** frame 12 faces screen-right, and frames advance clockwise in
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11.25° steps. In world terms, frame = 12 + (angle + 45°) / 11.25°.
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- **Tilt:** block = roll × 5 + pitch, each in 0..4, with 2 = level.
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Block 12 is the car on flat ground.
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- **Tilt:** block = roll × 5 + pitch, each in 0..4, with 2 = level. Block
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12 is the car on flat ground.
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The caravan (`caravan.aga`) uses the same layout. It's a trailer with a tow
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bar, not a car.
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`Police.aga` reads as all zeros with one third-party ADF tool, but it's
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intact when read directly from the disk image.
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### Settings (`vehicles/*.set`)
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- **Header:** the car's name and its driver's name, each followed by a
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newline.
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- **Settings:** 16 `u16` values. Eleven are used by the cars; the rest are
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zero. The caravan's values differ in kind; two of them are −4.
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- **Menu picture:** 512 bytes. A 64 × 32 picture in two bitplanes, plane 0
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(256 bytes) then plane 1.
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The settings are clearly handling values. The first is smallest for the
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Cow, the second largest for the F1, and the Police car and Porsche are
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nearly identical. What each one means lives in the executable and isn't
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decoded yet.
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## Sounds (`sfx/*.iff`, `gfx/*.iff`)
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Uncompressed IFF 8SVX, 8-bit signed, mostly at Amiga rates (8363 Hz and
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others). Looping sounds use the repeat part of `VHDR`. `gfx/` holds a few
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extra and alternative sounds (`crash1`, `crash2`, `engine`, `motor`,
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`screech`); `gfx/crash4.iff` isn't IFF.
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## Pictures (`gfx/*.iff`)
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IFF ILBM with ByteRun1 compression. `skidtoon.iff` is the 608 × 180,
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16-colour title picture; `chat2`, `mouse` and `sign` are small odds and
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ends. `ball.spr` (34816 bytes) is in another format and isn't decoded.
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## Music (`sfx/tune.crn`)
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A CrunchMania-packed OctaMED `MMD1` module: 4 tracks, 21 plain 8-bit
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sample instruments, 70 blocks played in order. The main song is positions
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0–65, ending with a jump back to the start. Positions 66–69 hold separate
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short pieces that end with "stop".
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The song uses these commands:
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- `1`, `2` (slide up, slide down)
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- `3` (portamento)
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- `9` (speed)
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- `B` (jump)
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- `C` (volume, decimal)
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- `D` (volume slide)
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- `F00` (break), `F1` (play twice), `F2` (delay), `FD` (set pitch),
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`FE` (stop)
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`src/music.rs` plays these. Its loudness tracks OpenMPT's rendering of the
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module second by second through the whole song (correlation 0.996 over the
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first minute), and it loops at the same point.
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## Executables
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- **`SKIDMARKS_CD³²`** (237 KB): a single-hunk compiled Blitz Basic 2
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program. It includes IFF ILBM/8SVX/ANIM loaders and a tracker replay
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routine with note-period tables.
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- **`skidmarks2`** (90 KB): a three-hunk program whose code is packed.
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## Gaps
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These almost certainly live on the missing disk 1:
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- The main executable, and with it the real handling model, AI, rules,
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menus and fonts. This port's versions are reconstructions.
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- Colour palettes. Neither the track nor the vehicle files carry any. The
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engine uses a reconstructed palette, and real ones can be dropped in as
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`.pal` files (see the README).
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- Sound effects and music.
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- Any tracks or vehicles beyond the 24 and 8 above.
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- **Game logic.** The handling, AI and rules in the executable aren't
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decoded; this port's versions are reconstructions. Decoding the `.set`
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values would be the first step towards the original handling.
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- **Unknown data:** the 12 bytes after each track file's palette, the bit
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pattern after the gates in each track section, the thumbnails, and
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`ball.spr`.
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The engine's own editable formats, which `skids extract` converts all of
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the above into, are described in [assets/README.md](../assets/README.md).
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If disk 1 turns up, put it next to the others and run `skids info`.
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Anything in a `track/` or `vehicles/` directory inside its archive is
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picked up automatically.
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