Replace C# parser stack with Rust FFI via redguard-preservation

[michidk]

Summary

Replaces the custom C# game file parsing pipeline with Rust FFI calls to redguard-preservation. Scene loading, model parsing, texture decoding, audio conversion, and subtitle loading all go through the native library. The entire legacy C# parser stack (~5900 lines) has been removed.

Performance

Full Island Scene Load (Stros M'Kai)

	C# Parser (master)	Rust FFI (this PR)
Total time	3,339 ms	848 ms
Meshes	3,000	3,000
Vertices	984,609	984,609
Triangles	328,587	328,587
Speedup	—	3.9×

Geometry output matches exactly. The FFI path also creates 556 point lights and flat sprite quads that the C# path previously skipped.

Changes

• Removed 15 legacy C# file parsers and 6 store classes (~5900 lines), replaced by a new Assets/Scripts/FFI/ layer with P/Invoke bindings, zero-copy deserializers, and cached loaders for models, textures, audio (SFX + RTX), loading screens, and world data
• Added Assets/Editor/RgprePluginDownloader.cs — editor tool to download rgpre binaries for all platforms from GitHub releases
• Added Assets/Plugins/rgpre/ — native plugin binaries organized by platform (Windows/x86_64/, Linux/x86_64/, macOS/arm64/, macOS/x86_64/)
• Updated WorldLoader, ModelViewer, GLTFExporter, and RGScriptedObject to route through the FFI adapters
• Kept gameplay runtime scripts (RGScriptedObject, RGObjectStore, RGRGMAnimStore, RGRGMScriptStore) — now populated from FFI data sources

Architecture

Game Files (.3D, .ROB, .RGM, .WLD, .TEXBSI, .GXA, .SFX, .RTX)
    ↓ file paths
rgpre.dll (Rust — stateless, path-based, internal texture cache)
    ↓ RGMD binary / RGBA pixels / WAV bytes / subtitle text
C# Adapters (FFIModelLoader, FFITextureLoader, FFISoundStore, ...)
    ↓ Mesh / Texture2D / Material / AudioClip
Unity Scene

FFI boundary — what crosses and what doesn't

The FFI layer (rgpre) handles all complex proprietary binary format parsing. The C# side only directly reads trivial/flat formats:

Access method	File types	Why
Through FFI (rgpre)	.RGM sections, .3D/.3DC/.ROB models, .WLD terrain, TEXBSI textures, .SFX/.RTX audio, .GXA animations, .FNT fonts	Complex proprietary binary container formats requiring structured parsing
Direct C# file I/O	WORLD.INI (text INI), .COL palettes (raw RGB bytes), config/save JSON	Trivial flat formats — no binary container logic needed

What the FFI currently covers

Domain	FFI functions	Output format
Meshes	rg_parse_model_data, rg_parse_rob_data, rg_parse_wld_terrain_data	Structured (RGMD — submesh headers + vertices + indices)
Scene	rg_parse_rgm_placements	Structured (RGPL — placements + lights with transforms)
Textures	rg_decode_texture, rg_decode_texture_all_frames, rg_texbsi_image_count, rg_decode_gxa, rg_gxa_frame_count	Structured (header + RGBA pixels)
Audio	rg_convert_sfx_to_wav, rg_sfx_effect_count, rg_convert_rtx_entry_to_wav, rg_rtx_entry_count, rg_get_rtx_subtitle	WAV bytes / UTF-8 subtitle text
Fonts	rg_convert_fnt_to_ttf	TTF bytes
GLB export	rg_convert_model_from_path, rg_convert_rgm_from_path, rg_convert_wld_from_path	Binary GLB
RGM sections	rg_rgm_section_count, rg_get_rgm_section	Raw section bytes

What's not yet covered — remaining C# parsing

The gameplay runtime scripts kept in this PR still do their own binary parsing from raw RGM section bytes. The Rust side already has parsers for all of this data — future FFI additions would let the C# side consume structured data instead of re-parsing the binary.

Data	What Rust parses today	What C# still parses	C# file
SOUP scripts	ActorScript — per-actor bytecode slice, resolved string table, variable table, script PC/offset/length from RAHD+RASC+RAST+RASB+RAVA	Full binary parsing of RAHD records, RASC bytecode extraction, RAST/RASB string resolution, RAVA variable loading	RGRGMScriptStore.cs (~55 KB)
SOUP386.DEF	SoupDef — 367 function names + param counts, flags, references, attributes, animation group names	Hardcoded function ID→name table and implementations	soupdeffcn_nimpl.cs (~79 KB)
RAGR animation groups	RagrAnimGroup — group index, anim ID, flag, frame count, command list	Binary parsing of RAGR section, group/command structures	RGRGMAnimStore.cs (~22 KB)
RAEX combat data	RaexRecord — grip points, scabbard slots, range min/ideal/max, taunt ID, texture ID	Binary parsing of RAEX records	Inline in RGM loading
RAVC collision volumes	RavcRecord — offset XYZ, vertex index, radius	Binary parsing of RAVC records	Inline in RGM loading
RTX label map	Script 4-char key → audio filename mapping	Not currently used — would connect SOUP dialogue calls to RTX audio files	—

Note: rg_get_rgm_section exists as an escape hatch to get raw section bytes for any RGM tag. The C# runtime scripts use this today. The goal for future FFI work is to replace those raw-byte consumers with structured data, so parsing lives in one place (Rust) and C# only runs the runtime/interpreter.

DLL Version

rgpre v0.5.1 — source: redguard-preservation