Convert RFA to ASAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read RFA files and write ASAT, 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 assembly
- Mixed geometry → exact geometry
- C++ / C# APIs
RFA to ASAT at a glance
Revit family can mix exact solids and facets; ACIS assembly stores exact geometry. Exact elements are written as exact geometry, and elements stored only as facets stay faceted.
| Revit family (source) | ACIS assembly (target) | |
|---|---|---|
| Full name | Revit family | ACIS assembly, text (ASAT) and binary (ASAB) |
| Standard / owner | Autodesk | Spatial (3D ACIS Modeler) |
| File extensions | .rfa | .asat, .asab |
| 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 |
| 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 ACIS assembly.
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Preserved
Exact geometryExact B-Rep read from RFA is written to ASAT as exact geometry.
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Preserved
Product structureThe RFA product structure is written to ASAT.
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Changes
Faceted partsParts the RFA file stores only as facets are written as facets.
Why software vendors add RFA to ASAT conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the ACIS assembly kernel. Writing ACIS assembly gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact ACIS assembly 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 assembly kernel often prefer to exchange ACIS assembly files directly.
Things to check before you ship
- Written ASAT 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 ASAT (.asat) file?
ASAT and ASAB are the assembly versions of the ACIS save file, in text and binary form. They store the product structure of models built on Spatial’s 3D ACIS Modeler kernel.
Frequently asked questions
The exact B-Rep that 3D InterOp reads from RFA is written to ASAT; parts stored only as facets stay faceted.
Yes. 3D InterOp reads the RFA product structure and writes it to ASAT.
An ACIS assembly (ASAT/ASAB) doesn’t support layers or colors at instance level, suppressed or hidden instances, or units at instance level.
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 ASAT to RFA is supported too.
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Building software that needs to convert RFA to ASAT?
3D InterOp is an SDK that lets your application read Revit family and write ACIS assembly alongside 30+ CAD and BIM formats.