Convert 3DM to ASAT in your application
3D InterOp is a CAD interoperability SDK that lets your software read 3DM files and write ASAT, 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 Rhino · Writes ACIS assembly
- Exact geometry → exact geometry
- C++ / C# APIs
3DM to ASAT at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| Rhino (source) | ACIS assembly (target) | |
|---|---|---|
| Full name | Rhinoceros 3D model | ACIS assembly, text (ASAT) and binary (ASAB) |
| Standard / owner | Robert McNeel & Associates | Spatial (3D ACIS Modeler) |
| File extensions | .3dm | .asat, .asab |
| Geometry | Exact NURBS geometry and meshes | Exact B-Rep |
| Assemblies / structure | No assembly hierarchy | Yes |
| 3D InterOp support | Read only | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from Rhino to ACIS assembly.
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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 3DM to ASAT conversion
Hand models to kernel-based applications
Many CAD, CAM and CAE applications are built on the ACIS assembly kernel. Writing ACIS assembly gives them exact geometry they can load without another translation step.
Downstream modeling and analysis
An exact ACIS assembly 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 assembly kernel often prefer to exchange ACIS assembly files directly.
Things to check before you ship
- Written ASAT versions: ACIS R18 to 2026 1.0.
- Supported 3DM input: Rhino 2 to 8.
- 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 3DM (.3dm) file?
3DM is the native file format of Rhinoceros (Rhino), the NURBS modeler from Robert McNeel & Associates. It stores exact curves, surfaces and solids, as well as meshes.
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Target 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.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
An ACIS assembly (ASAT/ASAB) doesn’t support layers or colors at instance level, suppressed or hidden instances, or units at instance level.
No. 3D InterOp reads Rhino geometry, but importing mapping data isn’t supported.
3D InterOp reads Rhino 2 to 8.
3D InterOp writes ACIS R18 to 2026 1.0.
No. 3D InterOp reads 3DM but doesn’t write it. To send data back to Rhino users, write a neutral format they can import, such as STEP.
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Building software that needs to convert 3DM to ASAT?
3D InterOp is an SDK that lets your application read Rhino and write ACIS assembly alongside 30+ CAD and BIM formats.