Convert ASAT to CATIA V4 in your application
3D InterOp is a CAD interoperability SDK that lets your software read ASAT files and write CATIA V4, with exact B-Rep geometry carried across and nothing tessellated.
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 ACIS assembly · Writes CATIA V4
- Exact geometry → exact geometry
- C++ / C# APIs
ASAT to CATIA V4 at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| ACIS assembly (source) | CATIA V4 (target) | |
|---|---|---|
| Full name | ACIS assembly, text (ASAT) and binary (ASAB) | CATIA Version 4 |
| Standard / owner | Spatial (3D ACIS Modeler) | Dassault Systèmes |
| File extensions | .asat, .asab | .model, .exp, .session |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes | Yes (written as parts only) |
| 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 ACIS assembly to CATIA V4.
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Preserved
Exact geometrySolids and surfaces stay exact B-Rep. The model is never reduced to a triangle mesh.
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Changes
Assembly flattenedThe CATIA V4 writer exports parts only: flatten the ASAT assembly into a single body before export, or the .model file is empty.
Why software vendors add ASAT to CATIA V4 conversion
Deliver in your customer’s CAD format
Aerospace and automotive OEMs often require supplier data in CATIA V4. Writing it lets your users meet that requirement directly from your application.
Exact geometry, ready to edit
CATIA V4 keeps exact B-Rep geometry, so the receiving engineer can measure, modify or machine the model in CATIA.
No neutral-format round trip
Writing CATIA V4 directly avoids an extra STEP or IGES step, and the loss each extra translation can add.
Things to check before you ship
- Written CATIA V4 versions: CATIA 4.1.9 to 4.2.4 (.model).
- The CATIA V4 writer isn’t available in 3D InterOp CGM.
- Supported ASAT input: ACIS R1 to 2026 1.0.
- 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 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.
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Target format
What is a CATIA V4 (.model) file?
CATIA V4 is the legacy generation of Dassault Systèmes’ CATIA, whose models are mostly stored in .model files. Many aerospace and automotive archives still hold CATIA V4 data.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
No. The CATIA V4 writer exports parts only: flatten the assembly into a single body before export, or the .model file is empty.
No. The CATIA V4 writer isn’t available in 3D InterOp CGM.
3D InterOp reads ACIS R1 to 2026 1.0.
3D InterOp writes CATIA 4.1.9 to 4.2.4 (.model).
Yes. 3D InterOp reads and writes both formats, so CATIA V4 to ASAT is supported too.
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Building software that needs to convert ASAT to CATIA V4?
3D InterOp is an SDK that lets your application read ACIS assembly and write CATIA V4 alongside 30+ CAD and BIM formats.