1. What the available evidence establishes
.MEF is a chunked model file used by Project I.G.I. 1. The repository’s common ILFF template and MEF parser/compiler represent a 20-byte outer header whose file type is OCEM. A 16-byte chunk header precedes each payload; the first chunk is not guaranteed by the container format to occur at a fixed offset.
The template/parser recognize model types 0, 1, and 3. The stride descriptions below are parser/template interpretations; this checkout does not include a retail asset corpus to independently validate every variant.
2. Container and chunk structure
The chunk link/skip field is used to traverse chunk data. FourCC labels identify payloads; they should not be mistaken for a single packed C++ struct shared by every model.
3. Vertex records and related chunks
| Chunk / record | Layout represented in template/parser | Evidence note |
|---|---|---|
XTRV, type 0 | 32 bytes: position (3 floats), normal (3 floats), UV (2 floats) | 8 float values |
XTRV, type 1 | 40 bytes: position, normal, UV, weight float, local vertex ID uint16, bone index uint16 | Skinning-related interpretation follows parser fields |
XTRV, type 3 | 40 bytes: position, normal, UV0, UV1 | Secondary UV begins at byte offset 32 in parser |
ECFC | 8 bytes per record: four uint16 fields | Triangle indices plus material/group field in parser |
ECAF | 6 bytes per record | Three uint16 indices |
ATTA | 68 bytes per record | Record size only; field semantics need file-level confirmation |
XTVC | 16 bytes per record | Template/parser layout |
XTVM | 16 bytes per record | Purpose is not established here |
4. Reading this specification
Sizes and offsets are useful for parsing, but semantic labels can be uncertain. Coordinates are scaled by some conversion paths; that does not establish the game’s native unit system. No claims are made here about a particular graphics API, draw-call pipeline, or exact model inventory.
Evidence: Templates/IGI1/IGI1_MEF.bt, Templates/common/ILFF.bt, and the IGI 1 converter’s mef_native.cpp / mef_compiler.cpp. See About for source links and verification limits.