PMob format reference

Status: implemented for the record families and traits documented below. Unrecognized records remain unsupported rather than being interpreted by name or file extension alone.

Binary structure

PMob is a little-endian recursive record tree. The file itself is the root PMob record; there is no separate magic signature.

Each record begins with:

Offset	Width	Meaning
0	4	Signed payload byte count
4	4	Signed child count
8	8 × count	Child entries: signed type ID and absolute file offset
after table	payload count	Record payload

Child records can appear elsewhere in the file and are addressed by absolute offset. Integers and IEEE-754 single-precision floats are little-endian. Names and texture strings are UTF-16LE. A transform matrix contains 16 floats.

Implemented record families include document identity, primitive hierarchy, animation transforms, layers, meshes, vertices, triangle indices, normals, UV coordinates, line indices, smoothing groups, material assignments, and observed material properties in type IDs 0x1a through 0x38.

Transform convention

The serialized convention is:

• 16 row-major floats;

• row-vector points (point * matrix);

• translation in M41, M42, and M43;

• local-to-world composition as local * parent; and

• Z as the up axis in supported assets.

Transposing each matrix produces Blender’s column-vector local matrix and normal parent @ local composition. Translation and mesh coordinates are converted from millimetres to metres at the Blender boundary. Linear matrix terms are not unit-scaled, so authored object scale is preserved.

Layer primitives reference geometry by layer name. The Blender adapter creates a mesh datablock once and instances it for each primitive reference.

Geometry and smoothing

Mesh indices describe consecutive triangles. Texture coordinates are one UV per serialized vertex when present.

The smoothing-group payload is a sequence of little-endian lists. Each list is a signed 32-bit vertex count followed by that many signed 32-bit indices. Negative counts, truncation, and out-of-range indices are invalid. These are vertex-membership groups, not conventional per-face smoothing-group numbers.

Producers can duplicate a position when adjacent face corners need different UVs, then place those indices in one smoothing group. Blender stores UVs and custom normals on face corners, so the importer can compact compatible smooth duplicates while retaining UV seams.

The reconstruction priority is:

1. Complete serialized normals.

2. Explicit smoothing groups, including omissions that preserve hard edges.

3. Authored vertex connectivity when neither source is available.

Position and face angle alone are not enough to distinguish a UV seam from a disconnected hard boundary. The importer therefore does not weld authored splits merely because their positions are equal. Resulting normals are written to face corners and compatible polygons use smooth shading.

PMob faces remain triangles. Optional Blender-side triangle-to-quad conversion joins only compatible, nearly coplanar pairs while checking UVs, materials, sharp/seam state, vertex colors, and shape quality. This is an editing convenience, not a PMob semantic, and is disabled by default.

Texture mapping

Some meshes omit serialized UV coordinates. Others contain UVs for an authored size but are later resized by package metadata.

For cubic mapping, material metadata supplies physical texture width and height in millimetres. Mooblender projects after primitive transforms and size correction, stores physical coordinates in metres on Blender’s corner domain, and derives UV scale from the material dimensions. Reusing a material therefore retains consistent texel density across differently sized parts.

Serialized UVs remain authoritative for non-cubic mappings. Fixed and planar MAPPING_SCALE values are normalized UV scales, not millimetre dimensions. Observed numeric mapping types are 0 fixed, 1 cubic, and 2 planar. Spherical variants are not established.

Materials

Material color payloads are four bytes in RGBA order. Supported packages can embed diffuse, metallic, and transparency images named by or derived from PMob material records.

• The diffuse image Alpha is multiplied by serialized material opacity.

• A separate transparency image is multiplied as an additional mask.

• The observed specular-texture channel maps to Principled Metallic.

• Normalized specular strength maps to Principled Specular IOR Level.

• Refraction factors above 1.0 are treated as optical IOR in supported material records.

Blender transmission depends on renderer settings. To keep refractive shells usable in default viewport and render configurations, Mooblender preserves IOR and uses bounded alpha blending as a fallback. It avoids accumulating opacity across overlapping transparent surfaces and retains supported ambient tint.

Exactly equal generated materials are reused. A material edited by the user is not silently replaced by a later import.

Safety validation

The reader validates record bounds, child counts, offsets, string lengths, matrix widths, index ranges, and recursive traversal before consuming payloads. Malformed data raises a format error rather than producing partial geometry.

Unknown or incomplete

• semantics for every mesh source type;

• line-index rendering rules;

• texture resolution outside PContent;

• animation time units and interpolation;

• spherical mapping variants; and

• compatibility across all PMob producer versions.