Convert RFA to SAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read RFA files and write SAT, 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 ACIS
- Mixed geometry → exact geometry
- C++ / C# APIs
RFA to SAT at a glance
Revit family can mix exact solids and facets; ACIS stores exact geometry. Exact elements are written as exact geometry, and elements stored only as facets stay faceted.
| Revit family (source) | ACIS (target) | |
|---|---|---|
| Full name | Revit family | ACIS model file (text SAT, binary SAB) |
| Standard / owner | Autodesk | Proprietary — Spatial (Dassault Systèmes) |
| File extensions | .rfa | .sat, .sab |
| Geometry | B-Rep and mesh (read); mesh (written by 3D InterOp) | Exact B-Rep |
| Assemblies / structure | Nested families; assembly structure written by 3D InterOp | Parts in SAT/SAB, assemblies in ASAT/ASAB |
| 3D InterOp support | Read and write | Read and write · ACIS R18 to 2026 1.0 |
What's preserved, what changes
Here is what your application can expect to carry across from Revit family to ACIS.
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Preserved
Exact geometryExact B-Rep read from RFA is written to SAT as exact geometry.
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Changes
Faceted partsParts the RFA file stores only as facets are written as facets.
Why software vendors add RFA to SAT conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the ACIS kernel. Writing ACIS gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact ACIS B-Rep can still be edited, meshed or machined by downstream tools, which a tessellated export would not allow.
Exchange within one ecosystem
Partners whose tools share the ACIS kernel often prefer to exchange ACIS files directly.
Things to check before you ship
- Written SAT versions: ACIS R18 to 2026 1.0.
- 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 an ACIS SAT file?
SAT is the native file format of 3D ACIS Modeler, Spatial's geometric modeling kernel used in CAD, CAM and CAE applications. It stores exact B-Rep models as text (.sat) or binary (.sab); ACIS assemblies use the .asat and .asab extensions.
Frequently asked questions
The exact B-Rep that 3D InterOp reads from RFA is written to SAT; parts stored only as facets stay faceted.
SAT has no assembly hierarchy, so your application decides how the RFA structure is grouped or flattened before writing.
Not above degree 25: ACIS doesn’t support B-spline geometry with a higher degree, so such geometry may be missing from the SAT file.
3D InterOp reads Revit 2015 to 2026.
3D InterOp writes ACIS R18 to 2026 1.0.
Yes. 3D InterOp reads and writes both formats, so SAT to RFA is supported too.
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Building software that needs to convert RFA to SAT?
3D InterOp is an SDK that lets your application read Revit family and write ACIS alongside 30+ CAD and BIM formats.