1. WorldMap terrain rendering and streaming
    1. Map layout recap
    2. Segment streaming (Wmx_UpdateSegmentStreaming, 0x5531F0)
    3. Runtime structures
    4. Per-frame rendering
    5. Address table

WorldMap terrain rendering and streaming

How the engine streams wmx.obj around the player and turns it into triangles each frame. Complements the wmx format and texl pages with the runtime view. Addresses for FF8_EN.exe, image base 0x400000.

Map layout recap

The world is a 32×24 grid of segments (8192 units each); a segment holds 4×4 squares (2048 units). Segment id = col + 32×row, toroidally wrapped. In wmx.obj a segment is a fixed 0x9000-byte record at offset 36864 × fileSegIdx — no compression.

Segment streaming (Wmx_UpdateSegmentStreaming, 0x5531F0)

  • The wanted set is rebuilt every frame: all segments within ±12287 units (up to a 4×4 area) of the look-ahead streaming center — a point 6144 units ahead of the camera (World_ComputeCameraLookAheadPoint), not the player itself.
  • Four linked lists of 12-byte nodes track state: pending → loading → loaded, plus a free list. Only one segment read is in flight at a time (async Archive_IO_LoadFile of 0x9000 bytes straight into a cache slot).
  • The cache has 16 slots; a new segment takes the first free slot, or steals the slot of a loaded segment no longer in the wanted set.
  • Alternate world states — story flags in wm_worldStateFlags (Fisherman’s Horizon bridge, the Lunar Cry crater, the shield around it, …) remap fileSegIdx through tables at 0xC763D2/0xC763EE (Wmx_ApplyAlternateSegmentRemap) before the read, which is how replacement segments stored later in wmx.obj appear transparently.
  • The same pump streams texl.obj detail pages: each segment header names its detail page (byte 0, 0xFF = none); two pages stay resident (0x12800 bytes each, uploaded as 128×256 texture + CLUTs). Pages 2/3 remap +12 under state flag bit 0 (post-FH-battle Horizon).

Runtime structures

Segment header: +0 texl detail page id, +4 int[16] block byte-offsets (one per square, index = x%4 + 4·(y%4), low 2 bits masked).

Block (one square): +0 u8 triangle count, +1 u8 vertex count, +2 u16 normal count, then 16-byte triangles, then 8-byte vertices (SVECTOR), then 8-byte normals.

Triangle (16 bytes):

Offset Meaning
0–2 vertex indexes
3–5 normal indexes
6–11 three U,V pairs
12 texture info: default = high nibble+224 → tpage, low bits → CLUT (UVs halved); with flag bit 5 = index into the animated-texture table; with bit 6 = texl detail page
13 terrain type (walkmesh material; also drives footstep/particle effects and script conditions)
14 flags: bits 0–1 shade level, bit 4 semi-transparent, bit 5 animated texture, bit 6 texl detail
15 vehicle walkability mask: bit 7 foot/chocobo, bit 6 buggy, bit 5 Ragnarok, bit 4 vehicle 49

Per-frame rendering

World_UpdateAndDrawTerrain_Fog (0x53BB90) or _NoFog (0x53C750, selected once per frame by the WORLDMAP_WITHOUT_FOG registry bit) orchestrates:

  1. Ground probes — 2 sets × 8 rows of 5 probes (44-byte records: world pos, segment-local pos, resolved triangle ptr, ground height, terrain type, state) are placed around the player/vehicles (World_SetupGroundProbeRow) and resolved against square blocks (World_ResolveGroundProbes, with an MRU triangle cache) using World_PointInTriangleGetHeight — an XZ point-in-triangle test with plane-interpolated height. This is the ground query every vehicle altitude/walkability check uses (World_IsTriangleWalkable tests the vehicle mask at tri+15).
  2. Visible square list — frustum-culled (World_CullVisibleSquareList) around the camera.
  3. Near blocks — full triangle emission per square (World_DrawNearBlock_*, with fog-overlay and Ragnarok-flight variants): vertices are camera-relativized and sunk by the horizon-curvature function (World_PretransformBlockVertices, curvature starts at wm_curvatureStartDist), projected (World_ProjectTerrainVertices), then emitted with per-triangle texture/CLUT selection and shade level.
  4. Far blocks — World_DrawFarTerrainBlock renders distant squares with the same curvature sink and texl detail LOD swap.
  5. Texture animation — beach/waterfall strips are advanced each frame by inline code in the world main loop (~0x540A8E) that updates the animated CLUT/tpage table and re-uploads 256×1 strips (wmsets41_parse).

Address table

Function Address   Function Address
Wmx_UpdateSegmentStreaming 0x5531F0   World_ResolveGroundProbes 0x53E2A0
Wmx_ApplyAlternateSegmentRemap 0x553980   World_PointInTriangleGetHeight 0x402620
Wmx_GetSquareBlockPtr 0x553E00   World_IsTriangleWalkable 0x53E6B0
Wmx_FindSegmentNode 0x553960   World_PretransformBlockVertices 0x4022D0
World_UpdateAndDrawTerrain_Fog 0x53BB90   World_ProjectTerrainVertices 0x4023D0
World_UpdateAndDrawTerrain_NoFog 0x53C750   World_SetupGroundProbeRow 0x53D8A0
World_DrawNearBlock_Fog / _NoFog 0x552380 / 0x553FD0   World_CullVisibleSquareList 0x53D3C0
World_DrawNearBlock_RagnarokFlight_Fog / _NoFog 0x5519B0 / 0x5543A0   wmx_segmentCache (16 slots) 0xC75D04
World_DrawFarTerrainBlock 0x5513A0   wm_worldStateFlags 0x2036BB6

Addresses are for FF8_EN.exe (2000 PC release) as mapped in IDA (image base 0x400000).