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.srl / .zsr — Per-Sector Sound Regions & Zones

Verified via reverse engineering

Traced live via GhidraMCP against FarCry2_server. Covers the container/attribution level — exact per-sector size, owning manager class, and grid indexing are confirmed; the internal record layout within each sector's blob is not (see Unknowns).

Two of the three files found alongside .sdat in every world sector (see .sdat's sibling-files note for the original hash-list discovery — 14,964 of each across the install, matching the sector count exactly): generated\worldsectors\sectorN.srl and generated\worldsectors\zonesectorN.zsr.

What the acronyms mean​

Both extensions are exported by name-obvious functions on CFCXEditorDocument (the map editor's own export driver, same class family that writes .sdat — see ExportSDAT there):

  • .srl = "Sound Region Layer" — written by ExportSoundRegionLayer (0x08cb1930).
  • .zsr = "Zone Sector" — written by ExportZones (0x08cb42a0-ish, caller of CZoneLogicManager::GetSectorData).

Container: none — a raw, fixed-size per-sector memory dump​

Unlike .sdat (a real chunked container with a header, metadata block, and record array — see .sdat), both of these are dead simple: a single fixed-size raw block per sector, written with no header and no framing at all.

// ExportSoundRegionLayer, one call per sector (x, y each 0..7):
void* data = CAmbianceManager::GetSectorData(x, y);   // this+0xb8, a grid of block pointers
file.Write(data, 0x400 /* = 1024 bytes, exact */);

// ExportZones, one call per sector (x, y each 0..7):
void* data = CZoneLogicManager::GetSectorData(x, y);  // this+0xdc, a grid of block pointers
file.Write(data, 0x1000 /* = 4096 bytes, exact */);
  • .srl is exactly 1024 bytes, always. CAmbianceManager::GetSectorData indexes a grid of pre-allocated block pointers at this+0xb8 by y * gridWidth + x — no per-sector size variation.
  • .zsr is exactly 4096 bytes, always. CZoneLogicManager::GetSectorData indexes a similar grid at this+0xdc, but — unlike ambiance — with an origin offset subtracted from both coordinates (this+0xf4/this+0xf6), meaning the zone grid isn't guaranteed to start at world sector (0,0).
  • Both confirm the same 8×8-sectors-per-level grid used everywhere else in this engine.

What's semantically inside each block​

Neither format's raw on-disk bytes were decoded field-by-field, but the class families that own this data give strong content-type context:

.srl (ambiance/sound regions) — a rich, time-of-day-driven soundscape system: SSoundRegion (the base record), SSoundRegionLevel (a volume/intensity level, sortable via SSoundRegionLevelSort), SSoundRegionTimeEntry/SSoundRegionTimeTrack (time-scheduled sound events, sortable via SSoundRegionTimeSort), SSoundRegionTimeRandomFx/SSoundRegionRandomFx/ SSoundRegionRandomFxSound (randomized ambient one-shots), SSoundRegionVirtualName (a named sound-bank reference), SSoundRegionTrackSetVolume (a volume-control track event) — SSoundRegionManager is the owning collection type.

.zsr (gameplay zones) — CZoneLogicRegion : CBasicRegionEntity is the per-zone record, which self-registers into CZoneRegionManager::AddRegion on construction and default-initializes three floats to 1.0 (offsets +0xe4/+0xe8/+0xec — plausibly an RGB tint or a scale/intensity triple, not confirmed). CZoneInfoComponent is the entity-side hook (an IEntityTask-style component, same pattern as every other per-entity capability documented in Engine Architecture) that presumably lets a placed entity define or query which zone it's in.

Unknowns​

  • The actual on-disk record layout for either format. SSoundRegion contains a std::string member (a name/virtual-name field) — a runtime C++ object with a heap pointer can't survive a direct memcpy-to-disk-and-back round trip, so the raw 1024-byte .srl blob is very unlikely to be a literal array of live SSoundRegion objects. Either there's a separate, flattened POD structure this data gets serialized to/from (not yet located), or CAmbianceManager's per-sector block holds something simpler than the full runtime record set and the richer SSoundRegion* family is reconstructed elsewhere at load time. Not resolved.
  • Whether .zsr's CZoneLogicRegion records serialize any more directly — CBasicRegionEntity's own fields weren't traced.
  • The exact meaning of CZoneLogicRegion's three default-1.0 floats.
  • Whether either file has any internal structure (record count, per-record size prefix) or is purely a fixed-layout struct array with a size implied entirely by the constant 1024/4096-byte total.