Convert STP to CATProduct in your application
3D InterOp is a CAD interoperability SDK that lets your software read STP files and write CATProduct, 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 CATProduct
- Exact geometry → exact geometry
- C++ / C# APIs
STP to CATProduct 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) | CATProduct (target) | |
|---|---|---|
| Full name | Standard for the Exchange of Product model data | CATIA V5 Product (assembly) |
| Standard / owner | ISO 10303 — AP203, AP214, AP242 | Dassault Systèmes |
| File extensions | .stp, .step | .CATProduct |
| Geometry | Exact B-Rep | Exact B-Rep (in the referenced parts) |
| Assemblies / structure | Yes | Yes |
| PMI | Graphical and semantic (AP242) | 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 STEP to CATProduct.
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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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Preserved
Product structureThe STP product structure is written to CATProduct.
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Improved
Healed geometry3D InterOp repairs and heals STEP data during translation.
Why software vendors add STP to CATProduct conversion
Deliver in your customer’s CAD format
Aerospace and automotive OEMs often require supplier data in CATProduct. Writing it lets your users meet that requirement directly from your application.
Exact geometry, ready to edit
CATProduct keeps exact B-Rep geometry, so the receiving engineer can measure, modify or machine the model in CATIA.
No neutral-format round trip
Writing CATProduct directly avoids an extra STEP or IGES step, and the loss each extra translation can add.
Things to check before you ship
- Written CATProduct versions: CATIA V5 R15 to V5-6 R2026.
- A CATProduct written by 3D InterOp can’t reference files in other formats.
- 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 CATProduct (.CATProduct) file?
A CATProduct file is a CATIA V5 assembly. It defines the product structure and positions, and references the CATPart files that hold the geometry.
Frequently asked questions
Yes. Both formats store exact B-Rep geometry, so the model is translated without being tessellated into triangles.
Yes. 3D InterOp reads the STP product structure and writes it to CATProduct.
No. A CATProduct written by 3D InterOp can’t reference files in other formats.
3D InterOp reads AP203, AP214 and AP242.
3D InterOp writes CATIA V5 R15 to V5-6 R2026.
Yes. 3D InterOp reads and writes both formats, so CATProduct to STP is supported too.
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Building software that needs to convert STP to CATProduct?
3D InterOp is an SDK that lets your application read STEP and write CATProduct alongside 30+ CAD and BIM formats.