TeslaRel410/dpl3-revive/spec/MAP_FORMAT.md

.MAP game maps and .MOD game objects

The actual playable game worlds — BattleTech arenas and Red Planet tracks — live in the game trees' MAPS/ directories (BTDAVE, BTLIVE, BTRAVINE, RPDAVE, RPLIVE), not in .SCN files. Reverse-engineered from the files themselves (INI-style text; ~50 maps, ~13,000 instance placements archive-wide).

.MAP

Sections declare assets; a type=map section places them:

[hall2]                     ; asset declaration
type=model
modelfile=hall2.mod
[one]
type=dropzone               ; pod spawn ring
dropzone= x y z  rx ry rz   ; rotations in RADIANS
[arena1]                    ; the map itself (usually named like the file)
type=map
instance=hall2  x y z  rx ry rz
instancedropzone=one  x y z  rx ry rz
[inc]
type=include                ; merge another .MAP's sections
file=other.map

• instance= may reference a model or another map section — maps nest, with transform composition (row-vector, Rz·Rx·Ry·T, unit scale — the SCN transform with radians instead of degrees).
• The root map section is the one named like the file (fallback: the map-typed section with the most instances).
• Comments: //. A leading [LAB_ONLY] marks unreleased content.

.MOD (game object)

[video]
object=rb3.bgf              ; render geometry (may carry a node name after it)
[collision]
name=rb3_cv.sld             ; collision volume (not needed for rendering)
[gamedata]
class=UnscalableTerrainClassID
; plus physics (mass, drag, friction), DamageZones, Explosion*, animation=,
; skeleton=, Subsystems= ... the full game-object layer (MechBld output)

For rendering, only [video] object= matters — take the first token, resolve the .BGF (DIV-BIZ2 geometry, see B2Z_FORMAT.md).

LOD container (format evolution, 1996)

Game-side BGFs nest their patches inside the LOD block (0x041), which the 1994 loader treated as an empty marker and skipped:

0x040 object
  0x036 vertex format
  0x041 LOD                ; now a CONTAINER
    0x046 len=8            ; switch in/out distances (2 × f32)
    0x042 patch ...        ; the actual geometry

A parser following the 1994 spec reads these files as empty. Parse the first (highest-detail) LOD's contents; later 0x041 blocks are lower-poly alternates and would double-draw. This unlocked ~850 game models that previously decoded to zero geometry.

Animation & effects

• A MOD's [video] object= list may carry several objects — e.g. the Red Planet door DRW.MOD: drw.bgf dr1.bgf dr2.bgf = frame + two sliding leaves ("number and order of objects is significant!"), plus low-poly LOD twins (<name>l, dropped for rendering). The wellhead WH1.MOD carries wh1.bgf … lazdril.bgf — the laser-drill beam mesh.

• Door motion is data, in the .SUB subsystems file:

  [door1]
  Type=DoorClassID
  TravelTime=13.0            ; seconds to open
  DeadTime=3.0               ; dwell at each end
  MotionExtent=-25.0 0.0 0.0 ; local slide vector
  Collision=dr1_cv.sld       ; links the subsystem to video object "dr1"
  

  The viewer plays this as a ping-pong slide (extent rotated into world space per instance). The laser drill's firing is engine-driven (no data), so the viewer gives laz* objects an approximate glow pulse — flagged as approximation.

• Scrolling textures play in maps too: any surface whose texture entity carries a SPECIAL=" SCROLL u0 v0 du dv" hook in its material library (smoke stacks, sky domes, beam effects) drifts its UVs — see SCN_FORMAT, Scrolling textures.

• Other animation carriers, not yet implemented: .ANI (INI skeletal keyframes: framecount/framerate/skeletonfile + .SKL skeletons — the mech walk cycles) and SPECIALFX particle-emitter definitions.

Asset resolution

Prefer assets from the same game tree as the map (<tree>/MODELS/*.MOD, <tree>/VIDEO/**.BGF) before the archive-wide basename index — BTDAVE, BTLIVE and BTRAVINE each carry their own versions.

Validation

ARENA1.MAP → the arena hall + 8 dropzones. CITY1.MAP → 77 placed buildings. BLADE.MAP (Red Planet) → 205 placements / 24k triangles; a render from its first dropzone shows the drop-station, canyon walls and track — the pod's-eye view. Dropzones are drawn as small red pyramids in the archive viewer.