VIS Homebrew

Homebrew development for the Tandy/Memorex Video Information System (VIS) — a 1992 multimedia console running Modular Windows 3.1 on an Intel 80286 @ 12 MHz, with a Yamaha YMF262 (OPL3) and a Mitsumi 1× CD-ROM.

The headline goal of this repo is a Wolfenstein 3D port running natively as a Win16 NE on Modular Windows VIS, rendered via GDI palette blits, with OPL3 audio over direct port I/O and hand-controller input.

Detailed per-session log: see VIS_sessions.md.

Status

Milestone	What it proves	Status
Hello World (S1)	Win16 toolchain + ISO + MAME boot path + CONTROL.TAT clone	✅
A.1 — Renderer foundation	Win16 chunky 320×200×8 + StretchDIBits + palette realization	✅
A.2 — Animation loop	DIB_PAL_COLORS fast path (5–6 FPS baseline)	✅
A.3 — Wolf3D palette	GAMEPAL.OBJ parser + 256-color grid on MAME VIS	✅
A.4 — VSWAP walls	Runtime asset loader from CD + 5 wall textures	✅
A.5 — VSWAP sprites	Sprite post format decoder + DrawSprite	✅
A.6 — HC input	Empirical VK_HC1_* codes (range 0x70..0x79) reverse-engineered	✅
A.7 — GAMEMAPS	MAPHEAD/Carmack/RLEW decompressors + minimap E1L1	✅
A.8 — OPL3	Direct port I/O 0x388/0x389 + sustained A4 note	✅
A.9 — Perf refactor	Static-bg snapshot + cursor erase/redraw + dirty-rect	✅
A.10 — IMF music	AUDIOT.WL1 / AUDIOHED.WL1 parser + IMF event scheduler over OPL3 (PoC)	✅
A.11 — Integrated scene	Walls + sprites + minimap + cursor + audio composited in one frame	✅
A.12 — Sprite scaler	Per-column post-walk fixed-point scaler over t_compshape sprites	✅
A.13 — Raycaster	Textured wall casting (DDA step-by-fraction) + ceiling/floor + player nav	✅
A.14 — Sprites in world	Static-decoration billboards over the cast scene + 1D z-buffer + painter's sort	✅
A.14.1 — Doors	DOORWALL texture + per-tile state machine + sliding slab + PRIMARY toggle	✅
A.15 — HUD	Wolf3D-style status bar with 7 panels + 4×6 digit font + face placeholder	✅
A.16a — Static enemies	Guard billboards (108..115 + 144..151 + 180..187) + 8-direction CalcRotate via atan2 LUT	✅
A.13.1 — Raycaster polish	Grid-line DDA + Tier-3 wall variety (32 pages, side-aware light/dark) + Watcom -ox discovery + time-scaled door anim + tight inner loops + partial-src StretchDIBits	✅
A.16b — Enemy AI ticker	State machine (Stand/Walk) + 32 walking frames + LOS Bresenham + 8-dir snap chase + sub-tile movement + per-axis collision + time-scaled phase advance	✅
A.17 — Weapon overlay	Vanilla SPR_PISTOLREADY blitted at viewport bottom-center, runtime chunk discovery (total_sprites - 15), 1:1 fixed-position blit via DrawSpriteFixed	✅
A.18 — Firing + hitscan + damage	PRIMARY rebind (door → SECONDARY), 4-frame ATK animation (PISTOLATK1..4 hot-swap), hitscan via z-buffer + first-hit screen-span scan, damage 5..12 + 3-frame DIE → frozen DEAD, ammo + score HUD partial re-blit	✅
A.15.1 — Real BJ face on HUD	VGAGRAPH chunked Huffman loader (VGADICT + VGAHEAD + VGAGRAPH), HuffExpand + 4-plane → linear deplane, FACE1APIC chunk 121 (empirical, not enum 113), 24×32 baked into static_bg, fallback to placeholder on load fail. Bundled fix: cardinal-angle DDA nudge for centre-column wall bleed	✅
A.19 — Centered viewport + minimap toggle (PF finale step 1)	VIEW_X0 0 → 96 (viewport horizontally centered), per-frame DrawMinimapWithPlayer removed (~25–30 ms/frame freed — H2 hot path captured), VK_HC1_F1 (Xbox X) toggles a 64×64 centered minimap overlay, music F1/F3 debug bindings dropped (OPL/IMF infra dormant). User confirms "QUASI giocabile" — first PoC milestone where the gameplay framerate becomes usable for real navigation	✅
A.19.1 — Sprite scaler Q.16 accumulator (PF finale step 2)	DrawSpriteWorld inner pixel loop converts per-pixel long division (sy_src = (dy - dy_top) * 64L / sprite_h) into a step_q16 = (64 << 16) / sprite_h step accumulator (sy_acc / srcx_acc) — same primitive as DrawWallStripCol. dy bounds pre-clipped once per post, framebuf access via decrementing __far pointer (no per-pixel multiplication). Eliminates the close-enemy freeze (sprite_h saturated at 4×VIEW_H = 512 was ~10 M cyc per sprite per frame → now ~250 k cyc). User: "il rallentamento con guardia vicina rimane, ma è meno bloccante rispetto a prima (nessun freeze, solo drop fps)" — H1 freeze closed; residual cost is linear pixel volume	✅
A.19.2 — Micro-perf bundle (PF finale step 3)	DrawWallStripCol ceiling/wall/floor fills do WORD pair-writes (single aligned word store replaces two byte stores: ~6 cyc/pair → ~3 cyc/pair on 286). DrawSpriteWorld outer column loop pre-clips dest_col to viewport and seeds srcx_acc so off-viewport iterations are skipped entirely; inner bound check dropped. EXE 229,736 B (slightly smaller than A.19.1 — pair-write loops compile to fewer instructions). User verdict shifts "QUASI giocabile" → "Giocabile", with residual close-quarter drop reframed by user as a non-realistic gameplay state ("le guardie sparano da lontano e un giocatore muore molto prima di raggiungerle da vicino"). Defensive: build batch now atomically copies EXE into cd_root_a21/ to prevent the recurring "shell missing → PROGMAN.EXE error" trap	✅
A.21 — DispDib direct A000 framebuffer + post-port polish	S17 disasm of DisplayDibCommon (file 0x154 of dispdib_raw.bin after correcting the runtime-loader segment-base bug) identifies BEGIN=0x8000 / END=0x4000 and supersedes the S16 NOWAIT=0x0100 misattribution (it was actually STRETCH 2X). KERNEL __A000H magic-constant export gives the runtime selector via (WORD)((DWORD)(LPVOID)&_A000H) — the OFFSET part of the far ptr IS the selector. WolfVis port replaces per-frame StretchDIBits + Select/RealizePalette with one-time DispDib BEGIN at startup + per-frame _fmemcpy(g_fb_a000, framebuf, ...) with bottom-up flip + DispDib END at WM_QUIT. Bonus polish: debug bar removed entirely (was the residual 500-ms heartbeat freeze via dirty-rect merge with InvalidatePlayerView); FireWeapon now returns BOOL so spam-at-zero-ammo / mid-animation taps don't trigger a wasted full-viewport redraw. EXE 229,102 B. Net: 7-8 FPS → 14-18 FPS (~2× speedup, dominant cost was GDI not raycaster) + freeze gone + spam fix. User verdict: "voglia di proseguire oltre le prime due guardie e stanze come invece fatto finora" — first time a build crosses from tech-demo to actually-engaging	✅
A.20 — Enemy fire-back + player health	New OBJ_ST_SHOOT 3-frame state (286 ms/phase, T_Shoot fires phase 0→1) wired into AdvanceEnemies chase trigger using vanilla T_Chase formula chance = (tics<<4)/dist. ShootPlayer reverse hitscan (LOS recheck + hitchance = 256-dist*8 + tiered damage). g_player_hp 0..100 with HUD HEALTH panel redraw (red below 25). On g_player_hp == 0: world freezes, PRIMARY taps trigger RestartLevel (reset hp/ammo/score/kills + re-spawn + full repaint). 8 subsystems, single-iter zero-fix. wolfvis_a20.c baseline	✅
A.20.1 — Combat fairness + damage flash polish	Hitchance softened from 256-dist8 (vanilla "not visible") → 160-dist16 (vanilla "visible") since LOSCheck-pass implies symmetric visibility = vanilla FL_VISABLE case where player has dodge window. Net: ~50% hit at dist=2 (was ~94%). Damage flash: 5-px red border (color 40 = HUD_FG_LOW) painted around viewport on first 2 of 3 ticks via g_damage_flash_ticks counter; final tick skips paint = clear-frame guarantee. WM_TIMER forces redraw while flash counter active so the sequence renders even on idle hit. User verdict: "fair (78/100 dopo due guardie)". wolfvis_a201.c baseline	✅
A.22 — Pickups (medkit / clip / treasures / 1up)	8 pickup kinds at obj_id 47..56 → VSWAP chunks 26-35: food (+10 hp), medkit (+25 hp), clip (+8 ammo), cross (+100), chalice (+500), bible (+1000), crown (+5000), 1up (+99 hp + 25 ammo). Object.pickup_kind BYTE field, ScanObjects pickup branch with switch (obj) for sparse mapping, CheckPickups same-tile proximity grab in WM_TIMER, TryGiveBonus with vanilla gates (hp==100 blocks health, ammo==99 blocks clip — pickup stays on floor). Removed pickups marked via sprite_idx = -1 (DrawSpriteWorld + painter sort short-circuit on negative). Trap caught: MAX_OBJECTS=128 overflow silently dropped guards in lower-y rows; bumped to 256, diagnosed via HUD-panel digit hijack (LEVEL/LIVES showing g_num_enemies/g_num_static at runtime). wolfvis_a22.c baseline	✅
A.23 — AdLib SFX subsystem (8 trigger points)	OPL3 ch0 SFX driven by 140-Hz frequency-byte stream from AUDIOT.WL1 chunks 69..137 (vanilla AdLib bank). LoadSfx(chunk_idx) parses 23-byte header (length + priority + 16-byte instrument + block) + body data. WriteSfxInstrument writes 11 OPL registers per vanilla SDL_AlSetFXInst (modifier op = reg 0, carrier op = reg 3, alFeedCon = 0). ServiceSfx PIT-direct accumulator (PIT_CYCLES_PER_SFX_TICK = 596400/140 = 4260) consumes 1 freq byte per tick: freq=0 = key off, else freqL + alBlock keyon. 8 trigger points wired (ATKPISTOL on FireWeapon, NAZIFIRE on ShootPlayer T_Shoot, HALT on WALK→SHOOT transition, DEATHSCREAM on lethal DamageEnemy, TAKEDAMAGE on DamagePlayer, GETAMMO/HEALTH/BONUS on TryGiveBonus). PeekMessage idle loop refactored: ServiceMusic + ServiceSfx after every Translate/Dispatch + ~14 mid-frame call sites (every 16 cols inside DrawViewport + post-render + mid-WM_TIMER) so accumulator never needs a cap (cap eats real time = "half speed", uncapped+sparse = bursty clicks; dense calls eliminate both). Bonus tool: tools/dump_sfx.py extracts AdLib chunks + renders via minimal pure-Python OPL2 emulator to WAV reference set in tools/sfx_dump/. A.23.2 follow-up bumped MOVE_STEP_Q88 24→64 (~2.7×) restoring vanilla RUN feel — was at exactly vanilla WALK speed (1.875 tile/sec) since A.6. User verdict: "Direi meglio ora!" + "Giocabilità molto migliorata"	✅

Repository layout

src/             Win16 / DOS sources (.c, .lnk, .bat) + ISO build scripts (.py)
reverse/         BIOS recon scripts (BIOS dumps and extracted CONTROL.TAT excluded — see Assets)
VIS_sessions.md  Per-session work log with approaches, traps, and discoveries
README.md        This file

The following directories are git-ignored — they are either fetchable, regenerable, or copyrighted third-party material:

• tools/ — Open Watcom V2 install (~537 MB; download from the project upstream)
• docs/ — Modular Windows SDK PDFs (Microsoft, 1992)
• assets/ — Wolfenstein 3D shareware data files (Apogee/id Software)
• wolf3d/ — local clone of the Wolf3D source for reference
• isos/ — retail VIS BIN/CUE images (Tandy/Memorex)
• vis.zip, reverse/p513bk*.bin — VIS BIOS extract (Tandy/Memorex)
• build/, cd_root*/, cfg*/, nvram/ — build outputs and MAME runtime state

Quick start

Dependencies

• Open Watcom V2 (Win16 toolchain). Install under tools/OW/ or anywhere — adjust the WATCOM env in the build_*.bat scripts.
• Python 3.10+ with pycdlib (pip install pycdlib) for ISO mastering.
• MAME 0.287+ with the vis BIOS (ROM set vis.zip containing p513bk0b.bin + p513bk1b.bin).
• VIS retail disc (any one) to generate a valid CONTROL.TAT for your homebrew ISO. The disc validation is non-cryptographic, so cloning the 12 binary "random" bytes from a retail TAT file is enough.
• Wolfenstein 3D shareware (*.WL1 files) placed under assets/ for the asset-driven milestones (A.4 onward).

Build the latest milestone

cd src
cmd /c ".\build_wolfvis_a23.bat"    # produces build/WOLFA23.EXE + stages it in cd_root_a23/
python mkiso_a23.py                  # produces build/wolfvis_a23.iso

Run on MAME

mame -rompath . vis -cdrom build/wolfvis_a23.iso -window -nomax -skip_gameinfo -nomouse

(Place vis.zip in the same -rompath directory.)

Generate CONTROL.TAT from a retail disc

cd reverse
python extract_tat.py path/to/RetailDisc.iso
python make_control_tat.py "MY HOMEBREW TITLE"

The output CONTROL.TAT goes into your cd_root_*/ staging directory next to AUTOEXEC, SYSTEM.INI, and your *.EXE.

Notes on third-party assets and copyright

This repository contains only original code and documentation authored for this project. It does not include:

• VIS BIOS dumps (p513bk0b.bin, p513bk1b.bin, vis.zip, reverse/dispdib_raw.bin) — copyright Tandy/Memorex.
• Retail VIS disc images (Atlas of Presidents, Bible Lands, Fitness Partner) — copyright Tandy/Memorex.
• Microsoft Modular Windows SDK PDFs — copyright Microsoft.
• Wolfenstein 3D shareware data files (VSWAP.WL1, GAMEMAPS.WL1, AUDIOT.WL1, etc.) — copyright Apogee/id Software.
• The Wolf3D source code clone used as a reference for porting (wolf3d/) — separately licensed under the GNU GPL by id Software (1995 release); fetch from id's official source release if needed.

You will need to source these files yourself to reproduce the build. Pointers are documented in VIS_sessions.md.

License

The original code in this repository (everything under src/ and reverse/*.py) is released under the MIT License unless otherwise noted.

Credits

• MAME vis driver authors (src/mame/trs/vis.cpp).
• VTDA for hosting the Microsoft Modular Windows SDK archive (MS37741_ModularSDK_Oct92).
• Open Watcom V2 maintainers for the only practical free Win16 toolchain in 2026.
• id Software for the Wolfenstein 3D source release.