Convert CATPart to SAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read CATPart files and write SAT, with exact B-Rep geometry carried across and nothing tessellated, without a CATIA license.
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 CATPart · Writes ACIS
- Exact geometry → exact geometry
- C++ / C# APIs
CATPart to SAT at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| CATPart (source) | ACIS (target) | |
|---|---|---|
| Full name | CATIA V5 Part | ACIS model file (text SAT, binary SAB) |
| Standard / owner | Dassault Systèmes | Proprietary — Spatial (Dassault Systèmes) |
| File extensions | .CATPart | .sat, .sab |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Part file (assemblies are CATProduct files) | Parts in SAT/SAB, assemblies in ASAT/ASAB |
| PMI | Semantic and graphical | PMI annotation classes |
| 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 CATPart to ACIS.
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Preserved
Exact geometrySolids and surfaces stay exact B-Rep. The model is never reduced to a triangle mesh.
Why software vendors add CATPart 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 CATPart input: CATIA V5 R8 to V5-6 R2026.
- 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 CATPart (.CATPart) file?
A CATPart file is a CATIA V5 part: one component with its exact 3D geometry, features and, often, PMI. Assemblies of parts are stored in CATProduct files.
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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
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
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.
No. 3D InterOp reads CATPart files directly, without CATIA or a CATIA license on the machine.
3D InterOp reads CATIA V5 R8 to V5-6 R2026.
3D InterOp writes ACIS R18 to 2026 1.0.
Yes. 3D InterOp reads and writes both formats, so SAT to CATPart is supported too.
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Building software that needs to convert CATPart to SAT?
3D InterOp is an SDK that lets your application read CATPart and write ACIS alongside 30+ CAD and BIM formats.