08-graphics-formats.md

08 — Graphics formats

All sizes below are after CrunchMania; regenerate the tree with python tools/crm.py -a _work/files -o _work/unpacked, then python tools/assets.py _work/unpacked. The full inventory is in notes/asset-inventory.md.

Everything the game draws is 8-bit chunky. The only planar data on the disc is the six pics/ screens, which are the front end.

pics/ — 7-bitplane screens, ByteRun1 inside CrunchMania

Twelve files: six images and six palettes.

offset 0   UWORD  width in pixels
offset 2   UWORD  height in rows
offset 4   UWORD  bitplanes
offset 6   UWORD  0
offset 8   ULONG  bitmap size = width/8 * height * planes
offset 12  IFF ByteRun1 (PackBits) stream

The bitmap is interleaved planar: planes consecutive rows of width/8 bytes per display line, which is what the copper's BPL1MOD = 6 * 40 requires.

File	Bytes	w	h	Planes	Declared bitmap	ByteRun1 gives
blackmagic	15,365	320	240	7	67,200	exact
combat	62,475	320	232	7	64,960	exact
gothic	59,932	320	240	7	67,200	exact
hell	59,592	320	240	7	67,200	exact
spacehulk	62,286	320	240	7	67,200	exact
theend	54,621	320	256	7	71,680	exact

All six unpack to their declared size to the byte, which is the check that the layout is right. The disc therefore compresses these twice: an IFF run-length encoder inside a Huffman-plus-LZ cruncher. On blackmagic — the publisher's logo, mostly black — the run-length layer alone takes 67,200 bytes to 15,353, because a blank 40-byte plane row encodes as the two bytes d9 00.

tools/pic.py decodes and renders one:

python tools/pic.py _work/unpacked/pics/spacehulk _work/files/pics/spacehulk.pal -o out.png

pics/*.pal — 128 entries of an AGA LOCT pair

512 bytes, and not 256 twelve-bit colours. Each entry is two big-endian words: the first carries the high nibble of each gun, the second the low, which is exactly how AGA's BPLCON3.LOCT pair is written and exactly how the copper builder at hunk 0x9c3c reads them (see 07-display-and-akiko.md).

gothic     entry 2 = 0fff 0fff  ->  R=ff G=ff B=ff
spacehulk  entry 1 = 0110 000c  ->  R=10 G=10 B=0c

Read as 256 single words the picture renders as noise. Read as pairs it renders. The first 32 entries of gothic, hell, combat and theend are the Deluxe Paint default 16-colour palette with every nibble doubled — a tell that the artwork came out of DPaint and never had its top end touched, which the credits (RENDERED IN DPAINT3 AND DPAINT4) agree with.

txts/ — chunky texture banks

Fourteen wall banks and six floor/ceiling tiles.

Wall banks (txt1_0..txt1_4, txt3_1..txt3_4, txt4_1..txt4_3):

offset 0    ULONG  offset of the palette
offset 4    N x 4160 bytes: one texture each
            4160 = 65 x 64  -- 64 rows of 65 bytes, or 64 columns of 65
palette     UWORD x N: 12-bit $0RGB, 0xFFFF = an unused slot

4,160 is the size the loader itself uses: the texture-bank loader at hunk 0x9f24 reads eight names out of a list, loads each, and walks the result with move.l #$1040,d1 (4,160) twenty times (moveq #$13,d0).

File	Bytes	Textures	Palette words	Used	0xFFFF
txt1_0	33,348	8	32	30	2
txt1_1	83,716	20	256	32	224
txt1_2	83,716	20	256	32	224
txt1_3	83,332	20	256	32	224
txt1_4	83,268	20	256	32	224
txt3_1	83,716	20	256	32	224
txt3_2	83,716	20	256	32	224
txt3_3	75,396	18	256	32	224
txt3_4	17,156	4	256	22	234
txt4_1	83,716	20	256	32	224
txt4_2	83,268	20	256	32	224
txt4_3	83,268	20	256	32	224

Nine of the twelve banks declare a 256-entry palette and fill 32 of it. The other 224 slots are FFFF FFFF FFFF … all the way to the end of the file. That is 448 bytes per bank, 5.4 KB across the disc, of a sentinel that means "empty" — the same shape as Legends' EMPTY PAL slots, in a format that spells it in hex. txt3_4 fills only 22 of its 256, and the texels in it never exceed 31.

Texel values run 0–31 with a handful of exceptions: txt1_1 uses 253 in 106 places, txt3_3 uses 251, 254 and 255, txt1_0 and txt4_1 use 255. Those are out of range for the 32-entry palette and are markers of some kind; what they mark is not settled here (see 12-open-questions.md).

Floors and ceilings (floor1..floor3, roof1..roof3) are all exactly 16,448 bytes with no header at all:

16,384 bytes  chunky, 128 x 128
UWORD         31   (the colour count minus one)
UWORD x 31    12-bit $0RGB

Texel values in them never exceed 28, and roof1 — a flat ceiling — packs from 16,448 bytes to 394, the best ratio on the disc.

objs/ — chunky sprite banks

Twenty files, and the header is unusually informative:

offset 0   UWORD  log2(number of rotations)      3 -> 8, 0 -> 1
offset 2   UWORD  number of animation states
offset 4   UWORD  maximum frame width
offset 6   UWORD  maximum frame height
offset 8   ULONG  bytes of frame data
offset 12  ULONG x (2^rot * states)  offsets to the frames
frames:
   UWORD  x anchor      UWORD  y anchor
   UWORD  width         UWORD  height
   BYTE[width*height]   chunky, 0 = transparent

2^rotations * states equals the number of offsets in the table on all twenty files, which is what confirms the first two fields:

File	Rotations	States	Frames	Max w x h
player	8	5	40	33 x 63
marine	8	5	40	34 x 64
baldy	8	6	48	38 x 64
demon	8	6	48	40 x 67
lizard	8	6	48	44 x 65
phantom	8	6	48	46 x 71
troll	8	6	48	65 x 69
terra	8	5	40	71 x 64
ghoul	8	3	24	55 x 85
deathhead	8	3	24	55 x 55
dragon	8	4	32	155 x 91
tokens	1	6	6	25 x 25
baldy2 … troll2	1	11–15	11–15	up to 72 x 56

The *2 files are the death animations: one viewpoint, eleven to fifteen frames, no rotations — a corpse does not need eight angles. tokens is the pickups. dragon is the largest asset on the disc at 340,456 bytes unpacked, 26 % of everything.

maps/ — 42 levels

21 single-player (map1_1..map1_7, map3_1..map3_7, map4_1..map4_7) and 21 two-player arenas (com1_1..com3_7).

offset 0    ULONG x 29   section offsets  (the first is 116 = 29 * 4)
section 0   8,192 bytes  = 64 x 64 UWORDs -- the level grid
sections 1.. variable-length lists; an empty one is four bytes

Every level file on the disc has exactly 29 sections and most of them are empty. map1_1 fills ten and leaves nineteen at four bytes each; across the 42 maps the count of non-empty sections runs from 5 (com1_1 and thirteen other arenas) to 29 (map3_6 alone). Sections 0, 1, 2, 4 and 5 are non-empty in all 42; sections 27 and 28 are used by one and two maps respectively. So the table is a fixed-width index over a variable-length object list, not a set of unused slots — a distinction worth making before calling anything a leftover.

Section 0, the grid, has 70 distinct values on map1_1, with 0xFFFF among them.

The level names come from misc/script, which addresses them as play_map1_1 and so on; the loader prefixes maps/. The combat arenas are built from a template string com1_1 at hunk 0x7e28 with the two digits patched in place.

misc/ — fonts and the script

bigfont.bin (10,820 bytes) and smallfont.bin (18,264) are offset tables followed by fixed-size glyphs (260 and 204 bytes each). The character mapper is in the executable at hunk 0x68c6 and maps A–Z to 9–34, . ! ? , to 36–39 and 0–9 to 0–9 — 40 glyphs, no lower case, and space handled separately as a cursor advance.

misc/script is plain ASCII and is quoted in full in 11-archaeology.md.