Unable to open .3MF from 3D Printing slicer

[LightDestory]

Describe the bug
F3D is not able to open, visualize, generate thumbnail for .3MF file generated by a slicer program (3D printing software).

I think that it is a customization of the .3MF file.

To Reproduce
Steps to reproduce the behavior:

1. Try to open the attached file

Expected behavior
Be able to preview the 3D content or visualize the static 2D png preview (common on such .3mf customizations).

System Information:

• OS: Windows 11
• GPU and GPU driver: NVIDIA RTX 2070S

F3D Information
F3D 3.3.0

F3D - A fast and minimalist 3D viewer
Version: 3.3.0.
Build date: 2025-10-22 15:21:13.
Build system: Windows 64-bits.
Compiler: MSVC 19.44.35217.0.
Module ImGui: ON.
Module OpenEXR: ON.
Module Raytracing: OFF.
Module WebP: ON.
VTK version: 9.5.2-1520-g01b47f3856 (date: 20251018).
Copyright (C) 2019-2021 Kitware SAS.
Copyright (C) 2021-2025 Michael Migliore, Mathieu Westphal.
License BSD-3-Clause.

Additional context
There files are generated by BambuStudio/Orca Slicer

Cube02ProfileMini.zip

[LightDestory]

If you extract the content of such .3mf file you can find static thumbnail inside the \Auxiliaries\.thumbnails directory.

The 3D data can be retrieved inside the 3D folder

[LightDestory]

The following python sample code converts .model file to a .obj:

import xml.etree.ElementTree as ET
import sys
from pathlib import Path

def convert_xml_to_obj(xml_file, obj_file):
    tree = ET.parse(xml_file)
    root = tree.getroot()
    ns = {'ns': 'http://schemas.microsoft.com/3dmanufacturing/core/2015/02'}

    if obj_file is None:
        obj_file = Path(xml_file).with_suffix(".obj")

    with open(obj_file, 'w') as f:
        mesh = root.find('.//ns:mesh', ns)
        if mesh is None:
            print("No mesh found in XML")
            return

        vertices = mesh.find('ns:vertices', ns)
        if vertices is not None:
            for vertex in vertices.findall('ns:vertex', ns):
                x = vertex.get('x')
                y = vertex.get('y')
                z = vertex.get('z')
                f.write(f"v {x} {y} {z}\n")

        triangles = mesh.find('ns:triangles', ns)
        if triangles is not None:
            for triangle in triangles.findall('ns:triangle', ns):
                v1 = int(triangle.get('v1')) + 1 # OBJ is 1-indexed
                v2 = int(triangle.get('v2')) + 1
                v3 = int(triangle.get('v3')) + 1
                f.write(f"f {v1} {v2} {v3}\n")

    print(f"Converted {xml_file} to {obj_file}")

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python model_to_obj.py <input.model> [output.obj]")
        sys.exit(1)
    in_path = sys.argv[1]
    out_path = sys.argv[2] if len(sys.argv) >= 3 else None
    convert_xml_to_obj(in_path, out_path)

[snoyer]

I haven't checked the provided file but we've seen issues with 3mf from BambuStudio/OrcaSlicer before due to the assimp library not handling model instancing/references: #1708

Upstream issue: assimp/assimp#5811

[mwestphal]

ERROR: In vtkF3DAssimpImporter.cxx, line 641
vtkF3DAssimpImporter (0x55be97b3d1e0): Assimp failed to load: /home/glow/data/tmp/Cube02ProfileMini.3mf


ERROR: In vtkF3DAssimpImporter.cxx, line 644
vtkF3DAssimpImporter (0x55be97b3d1e0): Assimp error: Validation failed: aiScene::mNumMeshes is 0. At least one mesh must be there


Some of these files could not be loaded: failed to load scene
  /home/glow/data/tmp/Cube02ProfileMini.3mf

Indeed, thats the same issue.
Since the other one on our repo is closed, I think we should keep this one open for visibility.