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IGI Reverse Engineering - Index

Legend

Marker Meaning
✅ Confirmed via hex dump or parser testing
⚠️ Partially known - structure documented but details unclear
❌ Unknown or not analyzed

Documentation Structure

reverse/docs/
├── 01-overview/          # Game info, structure
├── 02-executable/        # PE analysis, memory
├── 03-scripting/         # QVM bytecode
├── 04-rendering/         # Graphics pipeline
├── 05-ai-system/         # NPC behavior
├── 06-weapons/           # Weapon data
├── 07-terrain/           # Heightmap, tiles
├── 08-resources/         # ILFF format
├── 09-audio/             # Sound system
├── 10-menus/             # Menu system
├── 11-task-system/       # Task types
├── 12-level-system/      # Mission structure
├── 13-implementation/    # Implementation notes
├── 14-lod-system/        # LOD distances
├── 15-configuration/     # Config options
├── STATUS.md             # What we know vs don't know
└── INDEX.md              # This file

File Formats

Format Extension Header Payload Confidence Doc
ILFF .res ✅ Verified ⚠️ Edge cases unknown HIGH 08-resources
LOOP v8 .qvm ✅ Verified ⚠️ Bytecode partially mapped HIGH 03-scripting
LOOP v9 .tex ✅ Verified ⚠️ Pixel format unclear HIGH 07-terrain
LOOP v11 .res ✅ Verified ⚠️ Less tested MEDIUM 08-resources
MEF .res ⚠️ Nested structure ❌ Vertex layout unknown LOW 08-resources
Heightmap .bit ✅ Verified ⚠️ Flags inferred HIGH 07-terrain
Tile Centers .ctr ⚠️ Structure known ⚠️ Flags inferred MEDIUM 07-terrain
Tile Commands .cmd ❌ Unknown ❌ Unknown LOW 07-terrain
Lightmap .lmp ❌ Unknown ❌ Unknown LOW 07-terrain
Navigation .dat ✅ Magic verified ⚠️ Edge format partial MEDIUM 05-ai-system
QVM .qvm ✅ Verified ⚠️ Opcodes partial HIGH 03-scripting

Game Systems

System Status Confidence Key Unknowns Doc
Rendering ⚠️ Partially documented MEDIUM Vertex format, pipeline order 04-rendering
AI ⚠️ Partially documented MEDIUM Pathfinding algorithm, grid size 05-ai-system
Weapons ⚠️ Partially documented LOW Damage values, reload times 06-weapons
Terrain ⚠️ Partially documented MEDIUM Flag meanings, command encoding 07-terrain
Resources ⚠️ Partially documented HIGH Nested archive edge cases 08-resources
Scripting ⚠️ Partially documented MEDIUM Opcode table incomplete 03-scripting
Audio ⚠️ Partially documented MEDIUM Sample rate, bit depth 09-audio
Menus ⚠️ Partially documented MEDIUM Menu hierarchy reconstruction 10-menus
Tasks ⚠️ Partially documented MEDIUM Task descriptions inferred 11-task-system
Levels ⚠️ Partially documented MEDIUM Loading sequence inferred 12-level-system
LOD ⚠️ Partially documented MEDIUM Distance thresholds unverified 14-lod-system
Configuration ⚠️ Partially documented HIGH Runtime testing unverified 15-configuration

Document Summaries

01-overview

  • Game: Project IGI (1999)
  • Developer: Innerloop Studios
  • 14 missions + SHARED
  • ~1,972 files total
  • Engine version: 0.0.124 (from string analysis)

02-executable

  • PE32, MSVC 6.0 (from PE header)
  • EntryPoint: 0x004A4F85 (from PE header)
  • 4 sections: .text, .rdata, .data, .rsrc
  • DirectX 7 (from DLL imports)

03-scripting

  • QVM bytecode VM (structure verified, opcodes partial)
  • 22 events, 17 actions (from string analysis)
  • Event-driven architecture (inferred)
  • ~997 script files (from filesystem)

04-rendering

  • DirectX 7 (from DLL imports)
  • Terrain + models + particles + HUD (inferred from file types)
  • Pipeline order reconstructed, not verified
  • Triangle count unknown (estimated ~150K)

05-ai-system

  • Behavior tree architecture (inferred, not verified)
  • A* pathfinding (assumed, not confirmed)
  • 20-50 NPCs per level (estimated)
  • 3 difficulty levels (from configuration)

06-weapons

  • 21 weapons (from QVM analysis)
  • 8 categories (from QVM analysis)
  • 5 ammo types (from QVM analysis)
  • Damage values, reload times unverified

07-terrain

  • Heightmap: 16 bytes/entry (verified via hex dump)
  • Tile centers: 52 bytes/entry (partially verified)
  • Tile commands: binary encoding unknown
  • Lightmap: pixel format unknown

08-resources

  • ILFF container format (header verified)
  • IRESNAME + BODY pairs (structure known)
  • Nested archives for models (edge cases untested)
  • No compression/checksums (verified)

09-audio

  • DirectSound primary (from imports)
  • WINMM mixer (from imports)
  • RIFF/WAV format (standard assumption)
  • AVI cutscene playback (from imports)

10-menus

  • Screen stack system (reconstructed)
  • MenuManager API (from symbols)
  • 5 languages (from filesystem)
  • Content control (from symbols)

11-task-system

  • 64 task types (from string analysis)
  • Descriptions inferred from names
  • Vehicle hierarchy assumed
  • Hit multipliers unverified

12-level-system

  • 9 missions documented (from filesystem)
  • Loading sequence reconstructed
  • Navigation graph structure partial
  • Terrain grid 64x64 (from file size)

13-implementation

  • Format confidence levels assessed
  • Implementation roadmap provided
  • Open questions listed
  • See STATUS.md for unknowns

14-lod-system

  • ~400 models (from LOD.QVM)
  • 5 LOD levels + cutoff
  • Category ranges inferred
  • Distance thresholds unverified

15-configuration

  • Graphics/sound/input settings (from symbols)
  • Key bindings documented (from config)
  • Player profiles (from symbols)
  • Difficulty levels (from config)

Known Issues

  1. MEF vertex format - Chunk IDs known, vertex layout completely unknown
  2. Texture UV mapping - No UV coordinates documented
  3. Lightmap format - Pixel format, UV mapping, blending all unknown
  4. QVM opcodes - Only partially mapped, many opcodes unidentified
  5. Weapon parameters - Damage, timing, spread values are estimates
  6. NPC statistics - Health, damage, perception values are guesses

Legal

  • No game assets included
  • Static analysis only (no runtime verification)
  • For educational purposes
  • Users must own original game

Status

Static analysis done, runtime unknowns remain. No plans to continue engine development.

References

  • Original game: Project IGI (1999)
  • Developer: Innerloop Studios
  • Publisher: Eidos Interactive
  • Analysis tools: Hex dump, symbol analysis, string analysis