Convert DGN to SAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read DGN files and write SAT, 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 ACIS
- Exact geometry → exact geometry
- C++ / C# APIs
DGN 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.
| MicroStation DGN (source) | ACIS (target) | |
|---|---|---|
| Full name | MicroStation Design file | ACIS model file (text SAT, binary SAB) |
| Standard / owner | Bentley Systems | Proprietary — Spatial (Dassault Systèmes) |
| File extensions | .dgn | .sat, .sab |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes: models and references | Parts in SAT/SAB, assemblies in ASAT/ASAB |
| 3D InterOp support | Read only | 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 MicroStation DGN 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 DGN 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 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 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.
SAT has no assembly hierarchy, so your application decides how the DGN 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 DGN V7 to V8.
3D InterOp writes ACIS R18 to 2026 1.0.
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 SAT?
3D InterOp is an SDK that lets your application read MicroStation DGN and write ACIS alongside 30+ CAD and BIM formats.