1. Field rendering and collision runtime
    1. Background rendering
    2. Walkmesh and movement
    3. Triggers
    4. Characters, shadows, effects
    5. Address table

Field rendering and collision runtime

How the engine turns the field files into the running scene each frame: background tiles, depth, walkmesh movement, triggers and effects. The file formats themselves (.mim/.map/.id/.ca/.inf/.pmd) are documented in the Field File Format section; this page is the runtime view. Addresses for FF8_EN.exe, image base 0x400000.

Background rendering

  • Texture caching — the .mim is blitted into the emulated 1024×512 PSX VRAM (base 0x1B46618): palettes at (0,232), tile pixels as 16 strips of 832×16 from y=256. The generic psxvram layer converts texture pages to DirectX surfaces on demand.
  • Tile list — Field_BG_BuildTileDrawList (0x475480) re-walks the raw .map records (16 bytes/tile) every frame, emitting a 16-byte sprite primitive per visible tile (with DR_TPAGE prims on texture-page changes) into double-buffered prim buffers.
  • Scroll and parallax — per-layer screen position = tile.xy + camera pan × parallax/256 + script scroll; .inf byte 15 is the parallax-enable mask and .inf+22 holds per-layer wrap sizes (layers wrap when scrolled out of bounds). The whole-screen pan is applied as display-environment offsets (Field_BG_UpdateScreenScroll, includes shake).
  • State/animation tiles (doors, lights) — tile byte 14 = state group, byte 15 = state value; a tile draws only when its value matches the group’s current state in the 4-byte/group table at 0x1A77238 ({R,G,B,state}). The RGB part is tweened by controller structs (current/target color + timer) — this is BGANIME/light-flicker. Door triggers flip the states through script entity flags.
  • Depth — one Z ordering table per frame (0..4095, inside the double-buffered render context): tiles insert at their .map Z, character polygons and shadows insert at GTE-projected Z — so per-tile occlusion of characters costs nothing.
  • FMV fields — .inf byte 14 = 1 makes Field_BG_CaptureVramForMovieMask snapshot the background and the .msk file keeps foreground tiles above the movie.

Walkmesh and movement

Triangles are 24 bytes (3 × int16 xyz verts) with a 3×int16 adjacency table and a script-lockable per-triangle blocked bitfield. Entities (612-byte structs) carry fixed-point position, current triangle, collision radius, speed scale and facing.

  • Movement step (Field_Walkmesh_MoveEntityStep, 0x479C60): probes facing ±32 and straight rays with slope-attenuated speed; each ray also runs the entity-vs-entity cylinder test; the entity auto-rotates ±8 toward the free ray — that’s the wall slide.
  • Triangle transitions (Field_Walkmesh_ResolveMovement, 0x47A3E0): 2D cross-product edge tests; leaving an edge hops to the adjacency neighbor unless it is −1 or blocked (wall + slide hint). Height always comes from the triangle plane equation — smooth slopes and stairs.
  • Entity collision (Field_Collision_EntityVsEntities, 0x47A720): cylinder test on summed radii with height difference < 128; sets the touched flag consumed by TOUCH script events; through/push flags respected.

Triggers

  • Gateways (field exits, .inf+100, 12×32 B): line P1/P2, destination X/Y, destination walkmesh triangle, destination field id (< 0x48 = world map) and facing. A gateway fires when the player is within touch radius and the cross-product sign against the line flips between the old and new position. Spawn placement on the destination field uses the stored triangle (Field_Walkmesh_PlaceEntitiesOnLoad).
  • LINE triggers (script LINE/LINEON): lines live in the script-entity structs; Field_Collision_UpdateLineTriggerFlags (0x4775C0) latches WITHIN/LEAVE/CROSS/TOUCH/TALK/PUSH event flags that the script dispatcher consumes. Talk/push additionally require facing within 64/256 angle units and a button edge while stationary.
  • Door triggers (.inf+484, 12×16 B, modes 0–5): raise open/close request flags on the target script entity (Field_Collision_FireDoorTrigger) — sliding doors and background state flips.

Characters, shadows, effects

The .ca camera is parsed per frame; characters are posed (with head-tracking clamped to per-entity max angles) and rendered into the shared ordering table at projected Z. Circle shadows are 8 projected octagon segments with per-vertex radius/darkness. The PMD particle layer runs 16 emitters (254 B each) spawning into 128 particle slots of 32 bytes, camera-transformed as sprites (Field_FX_*, 0x473C50–0x4743D0); save/draw-point pulses are 8 dedicated slots gated by the SetSavePoint state.

Address table

Function Address   Function Address
Field_MainLoop_UpdateFrame 0x4767B0   Field_Walkmesh_MoveEntityStep 0x479C60
Field_BG_BuildTileDrawList 0x475480   Field_Walkmesh_ResolveMovement 0x47A3E0
Field_BG_UpdateScreenScroll 0x476450   Field_Walkmesh_HeightOnTriangle 0x47A680
Field_BG_UpdateScreenFade 0x47B980   Field_Walkmesh_PlaceEntitiesOnLoad 0x477C90
Field_BG_CaptureVramForMovieMask 0x472A60   Field_Collision_EntityVsEntities 0x47A720
Field_Chara_UpdateEntitiesMotion 0x4789A0   Field_Collision_UpdateLineTriggerFlags 0x4775C0
Field_Chara_SetModelPoseAndHeadLook 0x472B30   Field_Collision_CheckGatewayCrossing 0x477980
Field_Chara_DrawCircleShadows 0x472F20   Field_Collision_CheckInfDoorTriggers 0x47B610
Field_FX_UpdateParticleEmitters 0x473DE0   Field_Collision_CheckTalkPushButton 0x4777F0

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