Location

include/mop/loader.h       — Public API (MopBinaryMesh, mop_binary_load/free)
src/loader/mop_loader.c    — Loader implementation
tools/mop_convert.c        — OBJ-to-.mop converter CLI

Overview

The .mop format is a compact binary mesh format designed for fast loading. On POSIX platforms (Linux, macOS) the file is memory-mapped for zero-copy access — vertex and index pointers point directly into the mapped region. On other platforms a malloc + fread fallback is used.

File Layout

Offset   Size          Content
───────────────────────────────────────────────────
0        128           Header (MopBinaryHeader)
128      V * stride    Vertex data (MopVertex[])
128+V*s  I * 4         Index data (uint32_t[])

Where V = vertex count, I = index count, stride = sizeof(MopVertex).

Header (128 bytes)

Offset  Size  Type       Field           Description
──────────────────────────────────────────────────────────
0       4     uint32_t   magic           0x4D4F5001 ('M','O','P',0x01)
4       4     uint32_t   version         1
8       4     uint32_t   flags           Reserved (0)
12      4     uint32_t   vertex_count    Total vertices
16      4     uint32_t   index_count     Total indices (multiple of 3)
20      4     uint32_t   submesh_count   >= 1
24      4     uint32_t   vertex_offset   Byte offset to vertex data
28      4     uint32_t   index_offset    Byte offset to index data
32      12    float[3]   bbox_min        AABB minimum (x, y, z)
44      12    float[3]   bbox_max        AABB maximum (x, y, z)
56      72    uint8_t[]  _reserved       Zero-padded to 128 bytes

All values are little-endian. The header is exactly 128 bytes for cache-line alignment.

Vertex Layout

Vertex data uses the MopVertex struct layout directly:

typedef struct MopVertex {
    MopVec3  position;    /* 12 bytes */
    MopVec3  normal;      /* 12 bytes */
    MopColor color;       /* 16 bytes (4 floats) */
    float    u, v;        /*  8 bytes */
} MopVertex;              /* 48 bytes total */

On little-endian platforms the vertex data is used in-place from the mmap'd region — no parsing or byte-swapping required.

Index Data

Pre-triangulated uint32_t indices. The count is always a multiple of 3.

API

mop_binary_load

bool mop_binary_load(const char *path, MopBinaryMesh *out);

Opens and validates the file. On POSIX, uses mmap(MAP_PRIVATE). Sets out->is_mmapped = true on success. On non-POSIX platforms, allocates memory and reads the file.

Returns false on:

• NULL path
• File not found or too small
• Invalid magic number
• Unsupported version
• Data offsets exceeding file size

mop_binary_free

void mop_binary_free(MopBinaryMesh *mesh);

Unmaps or frees the mesh data. Zeroes the struct. Safe to call on a zeroed struct (no-op).

MopBinaryMesh

typedef struct MopBinaryMesh {
    MopVertex  *vertices;
    uint32_t    vertex_count;
    uint32_t   *indices;
    uint32_t    index_count;
    MopVec3     bbox_min, bbox_max;
    uint32_t    submesh_count;
    bool        is_mmapped;
    void       *_mmap_base;    /* internal */
    size_t      _mmap_size;    /* internal */
} MopBinaryMesh;

The vertices and indices pointers can be passed directly to MopMeshDesc for use with mop_viewport_add_mesh.

Converter Tool

# Build
make tools

# Convert OBJ to .mop
tools/build/mop_convert input.obj output.mop

The converter loads an OBJ file using mop_obj_load, writes the header, then writes vertex and index data contiguously.