Convert DGN to IGES in your application
3D InterOp is a CAD interoperability SDK that lets your software read DGN files and write IGES, 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 IGES
- Exact geometry → exact geometry
- C++ / C# APIs
DGN to IGES 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) | IGES (target) | |
|---|---|---|
| Full name | MicroStation Design file | Initial Graphics Exchange Specification |
| Standard / owner | Bentley Systems | ANSI |
| File extensions | .dgn | .igs, .iges |
| Geometry | Exact B-Rep | Exact B-Rep and surfaces |
| Assemblies / structure | Yes: models and references | No native assembly hierarchy |
| 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 IGES.
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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 structureIGES has no native assembly hierarchy. Decide in your application how MicroStation DGN product structure is grouped or flattened before writing.
Why software vendors add DGN to IGES conversion
Legacy CAD and CAM systems
Many established engineering tools still consume IGES first. Writing it lets your users hand data to them without leaving your application.
Supplier and partner exchange
Some suppliers and manufacturing partners still specify IGES in their exchange requirements. Your software can meet them directly.
Geometry-only workflows
When a downstream process needs exact part geometry and nothing more, IGES is a simple, widely readable target.
Things to check before you ship
- Written IGES versions: IGES 5.3.
- 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 IGES (.igs) file?
IGES is one of the earliest neutral CAD formats, an ANSI standard for exchanging 2D and 3D geometry. It stores exact curves, surfaces and solids, but not the product structure and manufacturing data STEP can carry.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
IGES has no assembly hierarchy, so your application decides how the DGN structure is grouped or flattened before writing.
3D InterOp reads DGN V7 to V8.
3D InterOp writes IGES 5.3.
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 IGES?
3D InterOp is an SDK that lets your application read MicroStation DGN and write IGES alongside 30+ CAD and BIM formats.