Convert 3DM to CATPart in your application
3D InterOp is a CAD interoperability SDK that lets your software read 3DM files and write CATPart, 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 CATPart
- Exact geometry → exact geometry
- C++ / C# APIs
3DM to CATPart 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) | CATPart (target) | |
|---|---|---|
| Full name | Rhinoceros 3D model | CATIA V5 Part |
| Standard / owner | Robert McNeel & Associates | Dassault Systèmes |
| File extensions | .3dm | .CATPart |
| Geometry | Exact NURBS geometry and meshes | Exact B-Rep |
| Assemblies / structure | No assembly hierarchy | Part file (assemblies are CATProduct files) |
| PMI | Not imported by 3D InterOp | Semantic and graphical |
| 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 CATPart.
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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 CATPart conversion
Deliver in your customer’s CAD format
Aerospace and automotive OEMs often require supplier data in CATPart. Writing it lets your users meet that requirement directly from your application.
Exact geometry, ready to edit
CATPart keeps exact B-Rep geometry, so the receiving engineer can measure, modify or machine the model in CATIA.
No neutral-format round trip
Writing CATPart directly avoids an extra STEP or IGES step, and the loss each extra translation can add.
Things to check before you ship
- Written CATPart versions: CATIA V5 R15 to V5-6 R2026.
- 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 a CATPart (.CATPart) file?
A CATPart file is a CATIA V5 part: one component with its exact 3D geometry, features and, often, PMI. Assemblies of parts are stored in CATProduct files.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
No. 3D InterOp reads Rhino geometry, but importing mapping data isn’t supported.
3D InterOp reads Rhino 2 to 8.
3D InterOp writes CATIA V5 R15 to V5-6 R2026.
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 CATPart?
3D InterOp is an SDK that lets your application read Rhino and write CATPart alongside 30+ CAD and BIM formats.