Dungeon Master Nexus Technical Reference

Status reviewed 2026-10-27. Japanese retail and English-version Ymir cold boots reach the native title menu; the English screenshot replay is pixel-exact. This is reference-emulator evidence only and does not make Nexus playable through Firestaff. The retail Japanese CUE/BIN drives a native MAPD title sequence. A capture-only NBG1 tile-fetch address correction is verified against an authentic startup frame in merged PR #19. Menu, HUD, dungeon composition and full playability remain open because each needs its own source-bound display consumer evidence.

Scope

Nexus targets the Saturn DMDF/DGN data family. The engine separates disc discovery, DMDF metadata, DGN geometry, static materials, startup/save routes, scripts, and audio. A parsable filename is never treated as source identity.

DGN Geometry

LEVxx.DGN parsing begins with typed Structure1B geometry. The renderer uses decoded floor, ceiling, and wall corner heights instead of flattening the world into a raw grid. Structure1F records retain verified ownership: direct items, floor decoration, and floor sensors are separate from Structure1A-bound alcove and wall records. Opaque fields do not become guessed draw/collision commands.

Static Materials

Static floor, ceiling, and wall commands consume paired retail SN_FLOOR.MNS and SN_WALL.MNS TEXT banks. Both canonical package receipts are required before decoded pixels reach the viewport. The MNS route has separate provenance from BPK; missing MNS data never authorizes a prefix import or flat fallback.

Structure2 descriptors are bounded provenance only until their payload and palette grammar are proved. Commands needing an unproved animated payload are no-draw.

MENU.BPK / PRS3

MENU.BPK PRS3 entries are inspected for bounded topology, mode, dimensions, and directory-trailer layout. The reviewed DMWeb DecodePRS3 byte grammar is implemented and verified against the real 20-frame FACE.BIN corpus. This is still not a Saturn presentation proof: MENU.BPK output remains no-draw until an original VDP1 capture binds decoded bytes to palette lane, placement, and command order. No synthetic PRS3 surface is admitted.

Gameplay Mechanics (Real-Data)

nexus_v1_mechanics_load_level() admits the active creature pool and hash-bound Structure1Fa floor items from authenticated LEVxx.DGN records. Structure1Fb floor decorations remain in the decoded raw DGN model; they are not registered as Vi altars because the model/aspect-to-altar and Saturn event joins are unproven. Door, pit, and other event semantics likewise remain capture-gated. The Structure1Fb declaration in include/nexus_v1_dgn.h (Nexus_V1_DgnFloorDecor) describes model/texture fields, not altar ownership; see docs/wiki/Nexus-DGN-and-PRS3-Internals.md, “Structure1B and Related Families.” NEXUS_CMD_USE_ITEM and combat mutations are not admitted for retail sessions without a Saturn action-owner receipt.

Verification: firestaff_nexus_v1_mechanics_playability_probe (real LEV files) and firestaff_nexus_v1_mechanics_parity_probe exercise this pipeline end to end; firestaff_nexus_v1_creature_state_determinism_probe checks creature-state determinism across runs.

Startup and Verification

Launcher startup carries title, save, champion, and package/host receipts into M11. Title readiness alone does not prove DGN rendering, SLEV/SAL sound, or Saturn timing. Retail TITLE.CG/MAPD assets are decoded and presented through a bounded route when their complete plane and palette receipt is admitted. MENU.BPK stays fail-closed awaiting PRS3 capture evidence; ACCEPT exits a completed title instead of trapping on the blocked menu route, and M11 presentation copies only source-bound material rather than substituting neutral placeholder colours.

nexus_v1_title_mapd_real reads TITLE.BIN and TITLE.CG through the native CUE/ISO reader when they are present only in the original Track 1 image. It uses bounded RAM buffers and does not require an extracted disc tree. The test source-binds all five MAPD/TIBG maps and their palette receipts. The bounded MAPD asset presentation consumes this admitted map sequence; it does not authorize the separate menu compositor, HUD or dungeon renderer, each of which still requires its own same-revision VDP consumer evidence.

cmake --build build --target test_nexus_v1_dgn_geometry_readiness \
  test_nexus_v1_dgn_material_raster test_nexus_v1_bpk_surface_class \
  test_nexus_v1_startup_menu_pc34_compat --parallel
./build/test_nexus_v1_dgn_geometry_readiness
./build/test_nexus_v1_dgn_material_raster
./build/test_nexus_v1_bpk_surface_class
./build/test_nexus_v1_startup_menu_pc34_compat

For DGN record ownership, MNS material provenance, Structure2, and PRS3 evidence, see Nexus DGN and PRS3 Internals.