Convert STL to 3MF in your application
3D InterOp is a CAD interoperability SDK that lets your software read STL files and write 3MF, carrying the mesh data across without re-tessellating it.
Spatial does not offer an online converter or a desktop conversion app. 3D InterOp is a component that software vendors embed in their own products.
- Reads STL · Writes 3MF
- Triangle mesh → triangle mesh
- C++ / C# APIs
STL to 3MF at a glance
Both formats store triangles, so the facets carry over without re-tessellation. The differences are in structure, appearance and metadata.
| STL (source) | 3MF (target) | |
|---|---|---|
| Full name | Stereolithography | 3D Manufacturing Format |
| Standard / owner | Open format | 3MF Consortium, ISO/IEC 25422 |
| File extensions | .stl | .3mf |
| Geometry | Triangle mesh | Triangle mesh |
| Assemblies / structure | No | Objects and build items |
| 3D InterOp support | Read and write | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from STL to 3MF.
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Preserved
Mesh dataThe STL facets are read and written to 3MF without being re-tessellated.
Why software vendors add STL to 3MF conversion
Additive manufacturing
3MF is still the input most slicers and print services expect. Writing it lets your users send parts to print directly.
Mesh-based processing
Inspection, scan comparison and mesh-editing tools work on triangles. A mesh output gives them a model they can open anywhere.
Lightweight sharing
A mesh is simpler than the native CAD file and needs no CAD system to open.
Things to check before you ship
- Written 3MF versions: 3MF 1.1.
- The 3MF writer is available through the UConnect interface only.
- Supported STL input: any STL version.
- Test tessellation settings on your heaviest parts: finer meshes mean larger files.
- Validate a sample of translated files in the target system your users actually work with.
Working with Spatial was a real milestone for us: Thanks to the powerful 3DInterOp library, we were able to successfully bring our complex CAD-based solutions to the cloud while remaining flexible to meet individual customer requirements. For us, Spatial is not just a technology partner, but a true enabler of our product strategy.
Dr. Arno Michelis, Founder, Simus Systems
Read the Case StudyAbout the formats
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Source format
What is an STL file?
STL describes a 3D surface as a set of triangles, with no units, materials or assembly structure. Its simplicity makes it the usual input for 3D printing.
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Target format
What is a 3MF (.3mf) file?
3MF is an open format for additive manufacturing, defined by the 3MF Consortium. It stores triangle meshes with units, colors and build information in a single package.
Frequently asked questions
No re-tessellation is needed. 3D InterOp reads the STL facets as visualization data and writes them to 3MF.
The 3MF writer is available through the 3D InterOp UConnect interface.
STL files store no units, so the 3D InterOp STL reader assumes millimeters. Agree on the unit with the application that wrote the file.
3D InterOp reads any STL version, as visualization data.
3D InterOp writes 3MF 1.1.
Yes. 3D InterOp reads and writes both formats, so 3MF to STL is supported too.
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Building software that needs to convert STL to 3MF?
3D InterOp is an SDK that lets your application read STL and write 3MF alongside 30+ CAD and BIM formats.