Convert CATIA V4 to CGR in your application
3D InterOp is a CAD interoperability SDK that lets your software read CATIA V4 files and write CGR, generating the CGR 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 CATIA V4 · Writes CGR
- Exact geometry → triangle mesh
- C++ / C# APIs
CATIA V4 to CGR at a glance
CATIA V4 stores exact geometry; CGR stores triangles. The translation is a tessellation, and the settings you choose decide how close the mesh stays to the original.
| CATIA V4 (source) | CGR (target) | |
|---|---|---|
| Full name | CATIA Version 4 | CATIA Graphical Representation |
| Standard / owner | Dassault Systèmes | Dassault Systèmes |
| File extensions | .model, .exp, .session | .cgr |
| Geometry | Exact B-Rep | Tessellated geometry |
| Assemblies / structure | Yes (written as parts only) | Single part |
| 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 CATIA V4 to CGR.
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Changes
Geometry is tessellatedThe exact CATIA V4 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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Changes
Assembly structureCGR has no native assembly hierarchy. Decide in your application how CATIA V4 product structure is grouped or flattened before writing.
Why software vendors add CATIA V4 to CGR conversion
Lightweight review
CGR 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 CGR file gives them the shape in a format their tools can open.
Easier handling of large assemblies
Without exact surfaces and feature data, CGR files are easier to transfer and display, even for large assemblies.
Things to check before you ship
- Written CGR versions: CATIA V5 R15 to V5-6 R2026, with the CATIA V5 writer.
- Supported CATIA V4 input: CATIA 4.1.9 to 4.2.4 (.model, .exp, .session).
- 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 CATIA V4 (.model) file?
CATIA V4 is the legacy generation of Dassault Systèmes’ CATIA, whose models are mostly stored in .model files. Many aerospace and automotive archives still hold CATIA V4 data.
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Target format
What is a CGR (.cgr) file?
CGR is CATIA’s lightweight graphical representation format. It stores a tessellated version of a part for fast display in large assemblies.
Frequently asked questions
3D InterOp tessellates the geometry it reads from CATIA V4 when it writes CGR. Your application sets the tolerances, so it controls the trade-off between accuracy and file size.
CGR has no assembly hierarchy, so your application decides how the CATIA V4 structure is grouped or flattened before writing.
No. 3D InterOp reads CATIA V4 files directly, without CATIA or a CATIA license on the machine.
3D InterOp reads CATIA 4.1.9 to 4.2.4 (.model, .exp, .session).
3D InterOp writes CGR files with its CATIA V5 writer, for CATIA V5 R15 to V5-6 R2026.
Yes. 3D InterOp reads and writes both formats, so CGR to CATIA V4 is supported too.
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Building software that needs to convert CATIA V4 to CGR?
3D InterOp is an SDK that lets your application read CATIA V4 and write CGR alongside 30+ CAD and BIM formats.