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What is a CATIA V4 file?

CATIA V4 is the fourth generation of CATIA, the CAD system developed by Dassault Systèmes. Its main file type is the .model file, which can contain 3D solids and surfaces, 2D drafting data and geometric sets, organized with layers and attributes. In CATIA V5, the equivalent of a .model part is the CATPart file.

CATIA V4 data relies on its own geometric representation, with analytic surfaces, polynomial surfaces and curves, and solid types such as SOLIDE and VOLUME. It also uses "ditto" entities to reuse geometry several times in a model, which is how assemblies are often represented in V4.


CATIA V4 file types

ExtensionContent
.modelThe main CATIA V4 file: part or assembly geometry, layers and attributes
.expExport archive that bundles several models, used to transfer data between sites
.sessionList of models loaded together in a work session, pointing to .model files rather than containing geometry

What Is CATIA V4 Used For? Applications and Industry Use Cases

Today, CATIA V4 files are mostly found in the long-lived programs of aerospace, automotive and their supply chains. Aircraft, vehicles and tooling designed in the 1990s are still maintained, modified and manufactured, and their original geometry is often stored only in V4 format.

For software developers, supporting CATIA V4 lets CAM, CAE, inspection and data management applications open this legacy data directly, without a CATIA license or a manual migration step. Some workflows also require writing .model files for partners that still use CATIA V4 output.


Challenges or Common Pitfalls

CATIA V4 data does not always map cleanly to modern B-rep kernels. Planes are unbounded in V4 and must be given limits on import, and surfaces or curves that are not smoothly continuous can arrive with closely spaced control points that need attention downstream.

Model history is not carried over, and some V4 content, such as dedicated assembly and drawing files or special layers used for dittos, may not be supported by a translator. Assemblies expressed through dittos also need a decision: keep them as an assembly or flatten them into a single model.

Because the format is old, finding a working CATIA V4 installation to re-export data is increasingly difficult, which makes direct, license-free reading more valuable over time.


How Spatial Helps

Our 3D InterOp SDK imports CATIA V4 .model (part and assembly), .session and .exp files and exports .model files, without requiring a CATIA license. The documented range covers CATIA 4.1.9 to CATIA 4.2.4 for both reading and writing, and the data can be translated into CGM Modeler, 3D ACIS Modeler or Parasolid.

On import, 3D InterOp extracts exact B-rep geometry and topology, including work planes and coordinate systems, and maps V4 analytic and polynomial geometry to the right analytic or B-spline equivalents. It reads the assembly tree with assembly-level names, and attributes such as name, color, layer, visibility, Pick/NoPick and identifiers, together with units, author, version and modification date. Layers and layer filters can be used to select which entities to read.

On export, you can set header information such as author, model name and language, and choose how solids are written: as SOLIDE or VOLUME, as faces or wires, or as separate sheet bodies. When translating from ACIS, analytic surfaces are approximated as polynomial surfaces to keep CATIA V4 files compact.

Dassault Systèmes

Siemens

Autodesk

Standards

Other

  • Pro/E / Creo
  • Rhino
  • MicroStation DGN
  • AVEVA
  • Smart3D

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