A .unv file is an I-DEAS Universal file. The format comes from SDRC I-DEAS, later owned by Siemens, and is plain text split into numbered blocks called datasets. Most UNV files you receive today are finite-element meshes: Salome, Code_Aster, CalculiX, Gmsh and several CFD tools write nodes, elements and named groups to it because almost every FE program can read it back.
You can open a UNV file in the CADProps workspace. It shows the mesh as an approximate triangle surface with the element edges, so you can look at the model, hide groups, check the bounding box, measure point-to-point distances and export STL, OBJ, GLB, glTF, 3MF or mesh STEP after sign-in. It is a mesh viewer for the file, not a solver or a CAD solid.
What is inside a UNV file
Each dataset starts and ends with a line containing -1, and the line after the opening marker holds the dataset number. The numbers tell you what the file carries:
| Dataset | Content | Shown in CADProps |
|---|---|---|
| 164 | Units | Used to verify the scale |
| 2411 (or 15, 781) | Node coordinates | Yes |
| 2412 (or 780) | Elements: beams, triangles, quads, tetrahedra, wedges, pyramids, hexahedra | Yes, as outer faces and straight beams |
| 2467, 2477 | Named groups of nodes or elements | Yes, as separate parts |
| 2414, 55, 56, 57 | Results, loads and analysis data | No |
| 1912, 801 and other CAD records | I-DEAS curves, surfaces and wireframes | Straight lines only |
Solid elements are shown by their outer boundary faces, so a tetrahedral mesh looks like the surface of the part rather than a cloud of internal cells. Quadratic elements are drawn through their corner nodes. Groups named in the mesher, such as an inlet, a wall or a fixed support, become parts in the model tree, which makes it easy to check that a boundary group covers the faces you expect.
Check the units before you measure
UNV coordinates have no fixed unit. When a file contains dataset 164, CADProps reads its length factor and converts the model to millimetres, and the scale is marked verified. Many exporters write SI units, so a CFD domain modelled in metres shows large millimetre values; a 1 m box reads 1,000 mm.
When dataset 164 is missing, coordinates are assumed to be millimetres. That is only an assumption: a mesh written in metres will then look 1,000 times too small. The file is marked as using assumed units, and area, volume and calculated mass stay unavailable. Measure one feature whose real size you know before you quote a dimension, and see the scale factor guide for common factors.
I-DEAS CAD records and other limits
Some older UNV files are I-DEAS part or assembly exports rather than meshes. They store curves and surfaces in CAD datasets. CADProps does not rebuild those surfaces; it shows only the explicit straight 3D lines it can identify, as a partial wireframe with a warning. Curved edges, faces, trimming and assembly placements are missing, so treat the result as a sketch of the outline and ask for STEP if you need the shape.
Other limits worth knowing:
- Results, loads, boundary conditions and materials are not displayed. Use your post-processor for stress or flow fields.
- Element types that are not in the table above are left out, and the warning lists their descriptor numbers.
- A wireframe-only file has no faces to export as a mesh.
- A triangle surface from an FE mesh is still a mesh. The tessellation guide explains why it cannot give back exact radii, and watertight meshes covers what volume needs.
The mesh format notes compare UNV with STL, OBJ, 3MF, glTF, VRML, X3D and AMF, and the format matrix lists every input and its limits.
Original article: CADProps · https://www.cadprops.com/guides/open-unv-file-online/