Struct ObjImporter 

pub struct ObjImporter;

Imports Wavefront OBJ files into 3MF Model structures.

Parses vertex positions (v) and faces (f) from OBJ text format. Polygonal faces with more than 3 vertices are automatically triangulated using fan triangulation.

Implementations

impl ObjImporter

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

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

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.

Format Details

• Index conversion: OBJ uses 1-based indices, converted to 0-based for internal mesh
• Fan triangulation: Polygons with N vertices create N-2 triangles using first vertex as fan apex
• Ignored elements: Texture coords (vt), normals (vn), groups (g), materials (usemtl, mtllib)
• Comments: Lines starting with # are skipped

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());
}