Convert STL to IFC in your application
3D InterOp is a CAD interoperability SDK that lets your software read STL files and write IFC, writing the STL facets as faceted geometry, since STL 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 STL · Writes IFC
- Triangle mesh → faceted model
- C++ / C# APIs
STL to IFC at a glance
STL stores triangles; IFC can hold facets alongside exact solids, so the mesh is written as faceted geometry.
| STL (source) | IFC (target) | |
|---|---|---|
| Full name | Stereolithography | Industry Foundation Classes |
| Standard / owner | Open format | buildingSMART, ISO 16739 |
| File extensions | .stl | .ifc, .ifczip |
| Geometry | Triangle mesh | Exact B-Rep and tessellated geometry |
| Assemblies / structure | No | Yes: spatial and element hierarchy |
| 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 IFC.
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Changes
Faceted geometrySTL stores triangles, so the IFC file holds faceted bodies, not solids. 3D InterOp doesn’t rebuild exact B-Rep from a mesh.
Why software vendors add STL to IFC conversion
Open BIM deliverables
Many projects specify IFC deliverables. Writing it lets your users meet those requirements from your software.
Coordination and clash detection
Coordination tools gather models from every discipline in IFC. Your users can contribute without a round trip through another tool.
Facility and asset data
Owners and operators often receive building data as IFC for asset management after handover.
Things to check before you ship
- Written IFC versions: IFC2x3 to IFC4x3 ADD2 (.ifc).
- Exact B-Rep needs IFC4 or later; IFC2x3 files only get tessellation.
- STL has no BIM semantics: check which IFC class your application assigns to each object.
- Supported STL input: any STL version.
- 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 an IFC (.ifc) file?
IFC is the open, vendor-neutral standard for exchanging building information models, maintained by buildingSMART and published as ISO 16739. It carries building elements with their geometry, properties and relationships.
Frequently asked questions
No. STL stores triangles, and 3D InterOp writes them to IFC as faceted geometry. It doesn’t rebuild exact B-Rep from a mesh.
Write IFC4 or later to keep exact B-Rep: IFC2x3 files only get tessellation. 3D InterOp writes IFC2x3 to IFC4x3 ADD2.
STL has no BIM semantics, so your application decides which IFC class each object is written as.
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 IFC2x3 to IFC4x3 ADD2 (.ifc).
Yes. 3D InterOp reads and writes both formats, so IFC to STL is supported too.
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Building software that needs to convert STL to IFC?
3D InterOp is an SDK that lets your application read STL and write IFC alongside 30+ CAD and BIM formats.