OpenCrossing-Dreamcast

A native Sega Dreamcast port of Animal Crossing (GameCube), built on the ACreTeam decompilation. Not an emulator — the decompiled game is recompiled for SH-4 and its GameCube graphics API is reimplemented on the PowerVR.

Target is a stock retail console: 16 MB RAM, no shaders, booting off a burned CD-R.

⚠️ Work in progress — not a playable game

It boots on real hardware and you can walk the town with music playing. That's about it. Do not expect to play Animal Crossing on this.

Working: boots on a retail Dreamcast (MIL-CD unit) and in Flycast. Title → intro → train → town → Nook's shop → house interiors. Music and sound effects. All 3,942 decomp objects build for sh-elf with no exclusions.

Not working: frame rate is ~16–23 FPS in Flycast and worse on hardware, which is the main problem. No saving — the VMU storage layer exists but the game's save path isn't wired to it. No villagers walking around; the game gates them behind Nook's first job and nobody has played that far at this frame rate. Some models and materials are missing, and the name-entry keyboard renders black.

Current numbers: kb/STATE.md. What's broken and in what order: kb/RESUME.md.

Game version: GAFE01 — Animal Crossing (USA), Rev 0. You supply your own disc image. Nothing ships here.

Building

Needs Docker, Python 3.9+, and your own GAFE01 ISO (1,459,978,240 bytes). The SH-4 toolchain, KallistiOS and the disc tools all live in the container.

The container is hardcoded to linux/arm64 and has only been run on an Apple-silicon Mac under colima. On x86-64 it'll fall back to qemu. A native amd64 image should work but has never been tried — start by dropping the --platform flags in dc/build-dc.sh and dc/build-dc-image.sh.

git clone https://github.com/GabeConway/OpenCrossing-Dreamcast
cd OpenCrossing-Dreamcast

# once, ~27 min: sh-elf-gcc + KallistiOS + mkdcdisc
bash dc/build-dc-image.sh

# pull the assets out of your ISO and flatten them into a disc root
make -C tools/dcasset extract ISO="/path/to/Animal Crossing.iso"
bash dc/stage-disc.sh /tmp/opencrossing-dc/discroot ~/.cache/oc-dc-discroot

# build
DC_STUB_KEEP="$(grep -v '^#' tools/dcstub/keeplist-full.txt | paste -sd: -)" \
DC_DISC_ROOT=~/.cache/oc-dc-discroot DC_ASSET_STUB=1 \
DC_ARAM_WINDOW=1048576 DC_ARENA_BYTES=1200000 \
DC_AUDIO_SCENES=all DC_AUDIO_DISC_FRAMES=8 DC_AUDIO_VOICES=12 \
bash dc/build-dc.sh

Use that build line, not a bare dc/build-dc.sh. Those variables aren't tuning — without DC_STUB_KEEP you get an image with about 53 KB of assets in it that boots, renders, and reports zero errors while being almost entirely empty. Check the build log says something like:

dc_stub_keep.inc: 3261 table rows + 2 .c_inc rows + 460 per-file init fns (2,929,360 B)

Output is dc/build/OpenCrossing.cdi. Open it in Flycast, or add DC_CDI_PAD=1 DC_CONSOLE_MUTE=1 and burn it to a CD-R for hardware.

Every target and knob: BUILDING-DC.md.

Don't distribute a built image — it contains Nintendo's assets.

Contributing

Frame rate is the top item and everything else is downstream of it. Other self-contained starts: the VMU save path, the 27 TEV configs that need a predicate narrowed, and hardware profiling (implemented, needs someone with a console and a CD-R).

The port lives in dc/; src/ is the decompilation and is never edited to make it compile — compat fixes go in the force-included dc/include/dc_prelude.h. kb/ is the knowledge base, dead ends included. Start at kb/RESUME.md, and read kb/closed.md and kb/traps.md before opening a PR. Renderer changes are judged on a matched-frame screenshot pair, not on counters.

Hall of Heroes

This port stands on the shoulders of:

• ACreTeam / ac-decomp — the complete C decompilation of Animal Crossing. Without it there is no port.
• Cuyler36 — the Ghidra GameCube loader, the save editor, and the reverse-engineering groundwork the decomp grew from; also the unlocked-FPS work upstream.
• flyngmt / ACGC-PC-Port — the original PC port: the GX→OpenGL layer and the keep-emu64 architecture this project inherits wholesale.
• Dia2809 — Linux support, the OpenGL ES renderer, and the ARM branches: the base the handheld port used.
• Falco Girgis — KallistiOS and sh4zam, the SH-4 math this port's transform path runs on, plus direction given directly to this project.
• OpenCrossing-Anbernic — the low-end-hardware port this one forked from.

The same names, in the same order, are on the boot screen.

Legal

Not affiliated with, endorsed by, or sponsored by Nintendo or Sega. "Animal Crossing" and related marks are Nintendo's, used here only to describe compatibility.

No disc image, ROM dump, or extracted asset ships in this repository. Supply your own legally obtained copy; the build reads it and never redistributes it. Images you build are for personal use only.

src/ is a decompilation — C source reconstructed from the retail game, published by ACreTeam under CC0. Nintendo authored neither it nor its license. The port layers (dc/, tools/, harness/dc/, kb/, pc/) are MIT. See LICENSE.

AI use

Claude (Anthropic) was used heavily in the making of this project.