Struct ObjImporter 

pub struct ObjImporter;

Imports Wavefront OBJ files into 3MF Model structures.

Supports two modes:

• read_from_path: Full import with MTL material resolution
• read: Geometry-only import (backward compatible, no materials)

Implementations

impl ObjImporter

pub fn read_from_path(path: &Path) -> Result<Model>

Reads an OBJ file from a filesystem path, resolving MTL files relative to it.

This is the recommended entry point for OBJ import. It resolves mtllib directives relative to the OBJ file’s parent directory, parses materials, splits groups/objects into separate 3MF Objects, and assigns per-triangle material properties.

Arguments

• path - Path to the OBJ file on disk

Returns

A Model containing:

• One [BaseMaterialsGroup] (if materials are referenced)
• One [Object] per OBJ group/object (or single Object if no groups)
• Per-triangle pid/p1/p2/p3 material assignment
• One [BuildItem] per Object

Errors

Returns errors for I/O failures or invalid OBJ syntax (see read).

pub fn read<R: Read>(reader: R) -> Result<Model>

Reads an OBJ file and converts it to a 3MF Model.

This is the backward-compatible entry point. No MTL file resolution is performed – material directives (usemtl, mtllib) are ignored. Group directives (g, o) are also ignored for full backward compatibility.

For material-aware import, use read_from_path.

Arguments

• reader - Any type implementing Read containing OBJ text data

Returns

A Model containing:

• Single mesh object with ResourceId(1) named “OBJ Import”
• All triangles from the OBJ file (polygons triangulated via fan method)
• All vertices from the OBJ file
• Single build item referencing the mesh object

Errors

Returns Lib3mfError::Validation if:

• Vertex line has fewer than 4 fields (v x y z)
• Face line has fewer than 4 fields (f v1 v2 v3…)
• Float parsing fails for vertex coordinates
• Integer parsing fails for face indices
• Relative indices (negative values) are used (not supported)

Returns Lib3mfError::Io if reading from the input fails.

Examples

use lib3mf_converters::obj::ObjImporter;
use std::fs::File;

let file = File::open("cube.obj")?;
let model = ObjImporter::read(file)?;

// Access the imported mesh
let obj = model.resources.get_object(lib3mf_core::model::resources::ResourceId(1))
    .expect("OBJ import creates object with ID 1");
if let lib3mf_core::model::Geometry::Mesh(mesh) = &obj.geometry {
    println!("Imported {} vertices, {} triangles",
        mesh.vertices.len(), mesh.triangles.len());
}