Convert RFA to STP in your application
3D InterOp is a CAD interoperability SDK that lets your software read RFA files and write STP, carrying across the exact geometry the RFA file contains.
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 Revit family · Writes STEP
- Mixed geometry → exact geometry
- C++ / C# APIs
RFA to STP at a glance
Revit family can mix exact solids and facets; STEP stores exact geometry. Exact elements are written as exact geometry, and elements stored only as facets stay faceted.
| Revit family (source) | STEP (target) | |
|---|---|---|
| Full name | Revit family | Standard for the Exchange of Product model data |
| Standard / owner | Autodesk | ISO 10303 — AP203, AP214, AP242 |
| File extensions | .rfa | .stp, .step |
| Geometry | B-Rep and mesh (read); mesh (written by 3D InterOp) | Exact B-Rep |
| Assemblies / structure | Nested families; assembly structure written by 3D InterOp | 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 Revit family to STEP.
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Preserved
Exact geometryExact B-Rep read from RFA is written to STP as exact geometry.
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Preserved
Product structureThe RFA product structure is written to STP.
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Changes
Faceted partsParts the RFA file stores only as facets are written as facets.
Why software vendors add RFA 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 RFA input: Revit 2015 to 2026.
- 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 RFA (.rfa) file?
An RFA file is a Revit family: a reusable component such as a door, a window or a piece of equipment, with its geometry, types and parameters, loaded into Revit projects.
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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
The exact B-Rep that 3D InterOp reads from RFA is written to STP; parts stored only as facets stay faceted.
Yes. 3D InterOp reads the RFA product structure and writes it to STP.
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.
3D InterOp reads Revit 2015 to 2026.
Yes. 3D InterOp reads and writes both formats, so STP to RFA is supported too.
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Building software that needs to convert RFA to STP?
3D InterOp is an SDK that lets your application read Revit family and write STEP alongside 30+ CAD and BIM formats.