Convert 3MF to STP in your application
3D InterOp is a CAD interoperability SDK that lets your software read 3MF files and write STP, writing the 3MF facets as faceted geometry, since 3MF stores triangles rather than solids.
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 3MF · Writes STEP
- Triangle mesh → faceted B-Rep
- C++ / C# APIs
3MF to STP at a glance
3MF stores triangles; STEP is an exact-geometry format. The mesh is written as faceted geometry: 3D InterOp doesn’t rebuild smooth surfaces from triangles.
| 3MF (source) | STEP (target) | |
|---|---|---|
| Full name | 3D Manufacturing Format | Standard for the Exchange of Product model data |
| Standard / owner | 3MF Consortium, ISO/IEC 25422 | ISO 10303 — AP203, AP214, AP242 |
| File extensions | .3mf | .stp, .step |
| Geometry | Triangle mesh | Exact B-Rep |
| Assemblies / structure | Objects and build items | Yes |
| PMI | None | Graphical and semantic (AP242) |
| 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 3MF to STEP.
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Changes
Faceted geometry3MF stores triangles, so the STP file holds faceted bodies, not solids. 3D InterOp doesn’t rebuild exact B-Rep from a mesh.
Why software vendors add 3MF to STP conversion
Supplier and OEM exchange
STEP is the ISO standard most supply chains specify for exchanging 3D models. Writing it lets your users send data to partners on any CAD system.
Model-based definition
STEP AP242 can carry semantic PMI next to exact geometry, so your users can share models together with their manufacturing data.
Long-term archiving
As an ISO standard independent of any CAD vendor, STEP is widely used to archive product data.
Things to check before you ship
- Written STP versions: AP203, AP214 or AP242 (.stp, .step or .stpx).
- Supported 3MF input: 3MF 1.1.
- 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 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.
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Target format
What is a STEP (.stp) file?
STEP is the ISO 10303 standard for exchanging 3D product data between CAD systems. Its application protocols range from exact geometry (AP203, AP214) to full model-based definition with PMI (AP242).
Frequently asked questions
No. 3MF stores triangles, and 3D InterOp writes them to STP as faceted geometry. It doesn’t rebuild exact B-Rep from a mesh.
The STEP writer supports AP203, AP214 and AP242, with AP214 as the default. Your application sets the version at export; semantic PMI is written to AP242 only.
Per-facet colors are imported. Textures and materials aren’t.
3D InterOp reads 3MF 1.1, as visualization data.
Yes. 3D InterOp reads and writes both formats, so STP to 3MF is supported too.
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Building software that needs to convert 3MF to STP?
3D InterOp is an SDK that lets your application read 3MF and write STEP alongside 30+ CAD and BIM formats.