Convert CATPart to OBJ in your application
3D InterOp is a CAD interoperability SDK that lets your software read CATPart files and write OBJ, generating the OBJ mesh from the geometry it reads, with tessellation settings your application controls, without a CATIA license.
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 CATPart · Writes OBJ
- Exact geometry → triangle mesh
- C++ / C# APIs
CATPart to OBJ at a glance
CATPart stores exact geometry; OBJ stores triangles. The translation is a tessellation, and the settings you choose decide how close the mesh stays to the original.
| CATPart (source) | OBJ (target) | |
|---|---|---|
| Full name | CATIA V5 Part | Wavefront OBJ |
| Standard / owner | Dassault Systèmes | Open format |
| File extensions | .CATPart | .obj |
| Geometry | Exact B-Rep | Polygon mesh |
| Assemblies / structure | Part file (assemblies are CATProduct files) | No assembly hierarchy |
| PMI | Semantic and graphical | None |
| 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 CATPart to OBJ.
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Changes
Geometry is tessellatedThe exact CATPart B-Rep is replaced by a triangle mesh, generated by 3D InterOp from the exact geometry it reads. Accuracy depends on the tessellation settings your application uses.
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Not carried
PMIOBJ has no place for PMI, so the PMI read from CATPart isn’t written.
Why software vendors add CATPart to OBJ conversion
Lightweight review
OBJ carries tessellated geometry that opens much faster than the full CAD model, so design reviews and digital mockups stay responsive.
Sharing outside engineering
Marketing, training and sales teams rarely have CAD software. A OBJ file gives them the shape in a format their tools can open.
Easier handling of large assemblies
Without exact surfaces and feature data, OBJ files are easier to transfer and display, even for large assemblies.
Things to check before you ship
- The OBJ writer is available through the UConnect interface only.
- Supported CATPart input: CATIA V5 R8 to V5-6 R2026.
- Test tessellation settings on your heaviest parts: finer meshes mean larger files.
- 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 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.
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Target 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.
Frequently asked questions
3D InterOp tessellates the geometry it reads from CATPart when it writes OBJ. Your application sets the tolerances, so it controls the trade-off between accuracy and file size.
OBJ has no place for PMI, so the PMI read from CATPart isn’t written. Your application can still access it after import, or offer STEP AP242 as an output.
The OBJ writer is available through the 3D InterOp UConnect interface.
No. 3D InterOp reads CATPart files directly, without CATIA or a CATIA license on the machine.
3D InterOp reads CATIA V5 R8 to V5-6 R2026.
Yes. 3D InterOp reads and writes both formats, so OBJ to CATPart is supported too.
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Building software that needs to convert CATPart to OBJ?
3D InterOp is an SDK that lets your application read CATPart and write OBJ alongside 30+ CAD and BIM formats.