Convert OBJ to CATPart in your application
3D InterOp is a CAD interoperability SDK that lets your software read OBJ files and write CATPart, writing the OBJ facets as faceted geometry, since OBJ stores triangles rather than solids.
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 OBJ · Writes CATPart
- Triangle mesh → faceted B-Rep
- C++ / C# APIs
OBJ to CATPart at a glance
OBJ stores triangles; CATPart is an exact-geometry format. The mesh is written as faceted geometry: 3D InterOp doesn’t rebuild smooth surfaces from triangles.
| OBJ (source) | CATPart (target) | |
|---|---|---|
| Full name | Wavefront OBJ | CATIA V5 Part |
| Standard / owner | Open format | Dassault Systèmes |
| File extensions | .obj | .CATPart |
| Geometry | Polygon mesh | Exact B-Rep |
| Assemblies / structure | No assembly hierarchy | Part file (assemblies are CATProduct files) |
| PMI | None | Semantic and graphical |
| 3D InterOp support | Read and write | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from OBJ to CATPart.
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Changes
Faceted geometryOBJ stores triangles, so the CATPart file holds faceted bodies, not solids. 3D InterOp doesn’t rebuild exact B-Rep from a mesh.
Why software vendors add OBJ 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 OBJ input: any OBJ version.
- 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 an OBJ (.obj) file?
OBJ is a simple, widely supported text format for polygon meshes, created by Wavefront. It describes vertices, faces and texture coordinates, with materials in a separate .mtl file.
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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
No. OBJ stores triangles, and 3D InterOp writes them to CATPart as faceted geometry. It doesn’t rebuild exact B-Rep from a mesh.
Yes. 3D InterOp reads the visual material properties of OBJ files on import.
3D InterOp reads any OBJ version, as visualization data.
3D InterOp writes CATIA V5 R15 to V5-6 R2026.
Yes. 3D InterOp reads and writes both formats, so CATPart to OBJ is supported too.
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Building software that needs to convert OBJ to CATPart?
3D InterOp is an SDK that lets your application read OBJ and write CATPart alongside 30+ CAD and BIM formats.