Convert DGN to CATIA V4 in your application
3D InterOp is a CAD interoperability SDK that lets your software read DGN 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 MicroStation DGN · Writes CATIA V4
- Exact geometry → exact geometry
- C++ / C# APIs
DGN 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.
| MicroStation DGN (source) | CATIA V4 (target) | |
|---|---|---|
| Full name | MicroStation Design file | CATIA Version 4 |
| Standard / owner | Bentley Systems | Dassault Systèmes |
| File extensions | .dgn | .model, .exp, .session |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes: models and references | Yes (written as parts only) |
| 3D InterOp support | Read only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from MicroStation DGN 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 DGN assembly into a single body before export, or the .model file is empty.
Why software vendors add DGN 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 DGN input: DGN V7 to V8.
- 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 DGN (.dgn) file?
DGN is the native design file format of Bentley MicroStation, widely used for infrastructure, plant and civil engineering projects. It exists in two generations, V7 and V8.
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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 DGN V7 to V8.
3D InterOp writes CATIA 4.1.9 to 4.2.4 (.model).
No. 3D InterOp reads DGN but doesn’t write it. To send data back to MicroStation users, write a neutral format they can import, such as IFC or STEP.
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Building software that needs to convert DGN to CATIA V4?
3D InterOp is an SDK that lets your application read MicroStation DGN and write CATIA V4 alongside 30+ CAD and BIM formats.