Convert STP to CATIA V4 in your application
3D InterOp is a CAD interoperability SDK that lets your software read STP files and write CATIA V4, 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 STEP · Writes CATIA V4
- Exact geometry → exact geometry
- C++ / C# APIs
STP to CATIA V4 at a glance
Both formats store exact geometry, so the model stays exact. The differences are in the product data each one can carry.
| STEP (source) | CATIA V4 (target) | |
|---|---|---|
| Full name | Standard for the Exchange of Product model data | CATIA Version 4 |
| Standard / owner | ISO 10303 — AP203, AP214, AP242 | Dassault Systèmes |
| File extensions | .stp, .step | .model, .exp, .session |
| Geometry | Exact B-Rep | Exact B-Rep |
| Assemblies / structure | Yes | Yes (written as parts only) |
| PMI | Graphical and semantic (AP242) | None in the format |
| 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 STEP to CATIA V4.
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Preserved
Exact geometrySolids and surfaces stay exact B-Rep. The model is never reduced to a triangle mesh.
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Improved
Healed geometry3D InterOp repairs and heals STEP data during translation.
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Changes
Assembly flattenedThe CATIA V4 writer exports parts only: flatten the STP assembly into a single body before export, or the .model file is empty.
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Not carried
PMICATIA V4 has no PMI, so the PMI read from STP isn’t written. Keep STEP AP242 as an output when PMI matters.
Why software vendors add STP to CATIA V4 conversion
Deliver in your customer’s CAD format
Aerospace and automotive OEMs often require supplier data in CATIA V4. Writing it lets your users meet that requirement directly from your application.
Exact geometry, ready to edit
CATIA V4 keeps exact B-Rep geometry, so the receiving engineer can measure, modify or machine the model in CATIA.
No neutral-format round trip
Writing CATIA V4 directly avoids an extra STEP or IGES step, and the loss each extra translation can add.
Things to check before you ship
- Written CATIA V4 versions: CATIA 4.1.9 to 4.2.4 (.model).
- The CATIA V4 writer isn’t available in 3D InterOp CGM.
- Supported STP input: AP203, AP214 and AP242.
- 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 STEP (.stp) file?
STEP is the ISO 10303 standard for exchanging 3D product data between CAD systems. Its application protocols range from exact geometry (AP203, AP214) to full model-based definition with PMI (AP242).
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Target 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.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
CATIA V4 has no PMI, so the PMI read from STP isn’t written. When PMI matters, offer STEP AP242 as an output.
No. The CATIA V4 writer exports parts only: flatten the assembly into a single body before export, or the .model file is empty.
No. The CATIA V4 writer isn’t available in 3D InterOp CGM.
3D InterOp reads AP203, AP214 and AP242.
3D InterOp writes CATIA 4.1.9 to 4.2.4 (.model).
Yes. 3D InterOp reads and writes both formats, so CATIA V4 to STP is supported too.
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Building software that needs to convert STP to CATIA V4?
3D InterOp is an SDK that lets your application read STEP and write CATIA V4 alongside 30+ CAD and BIM formats.