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Nexus Technical Reference
Status reviewed 2026-08-06. Nexus real-data parsing and several runtime slices are verified. Positive real-asset handoff and full playability remain open, especially for source-bound visible materials.
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.
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 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 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.
nexus_v1_mechanics_load_level() binds the active creature pool, pits,
altars, and doors from authenticated LEVxx.DGN records for the loaded map.
Creatures spawn from Structure1A actor records (type, position, and the
Z-rotation byte); unbound or hidden actors cannot move, attack, or take
damage until nexus_v1_creature_bind_actor_model() resolves them against MNS
roster metadata. Door open/close animation steps
(nexus_doors_tick_animation()) gate passability, and a candidate altar
registry (nexus_altars_register_tagged()) supports a fail-closed ritual
action. NEXUS_CMD_USE_ITEM consumes leader inventory slots (potions restore
stats; weapons/armor move to the matching equipment slot), and stepping on a
pit/chute square sets pending_level_change per ReDMCSB MOVESENS.C
semantics. Champion death auto-promotes the next living party member to
leader (ReDMCSB CHAMPION.C F0319_CHAMPION_Kill), matching total-party-death
handling when no successor remains.
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.
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. The real TITLE.CG reveal is drawable while 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 the source-bound material framebuffer rather than substituting neutral
placeholder colours.
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_compatFor DGN record ownership, MNS material provenance, Structure2, and PRS3 evidence, see Nexus DGN and PRS3 Internals.