Free online OFF to FCSTD converter

What the OFF format is

OFF, usually called the Object File Format, stores polygonal 3D geometry as vertices and faces. Its common ASCII structure begins with OFF, followed by counts for vertices, faces, and edges, then vertex coordinates and face index lists.

OFF is used for exchanging scanned meshes, computer-graphics models, polygon datasets, and computational-geometry examples. MeshLab, Geomview-related tools, CGAL-based programs, Blender through suitable export workflows, and custom geometry scripts can create or export OFF files. You typically encounter it when a model is supplied as a raw polygon mesh rather than as a CAD solid.

What the FCSTD format is

FCStd is FreeCAD's native document format. It can contain mesh objects, BRep shapes, sketches, Part Design bodies, feature history, views, and document metadata.

Saving an OFF mesh in an FCStd document makes it easier to manage in FreeCAD and combine with other document objects. Converting the mesh into a Part shape can also allow operations such as measurement, boolean processing, and export to formats supported by FreeCAD. The result is generally a faceted shape, not a fully editable parametric model.

How to convert OFF to FCSTD

Using FreeCAD

1. Install and open FreeCAD.
2. Choose File → Open and select the .off file. If the file is not listed, set the file filter to show all supported files or all files.
3. FreeCAD normally opens the data as a mesh object. Inspect it in the Mesh workbench and check that the scale, orientation, and face normals are correct.
4. To create a shape from the mesh, select the mesh in the Model tree, switch to the Part workbench, and choose Part → Create shape from mesh.
5. Set a tolerance appropriate to the model's units. A smaller tolerance preserves more detail but can increase processing time and memory use.
6. Optionally hide the original mesh and inspect the generated shape for holes, self-intersections, or missing faces.
7. Choose File → Save as, enter a filename such as model.FCStd, and save the FreeCAD document.

If retaining the original polygon object is useful, keep it in the document and save both objects. If only the converted shape is wanted, remove or hide the source mesh before saving.

Using 101convert

You can also convert the file on the 101convert website for free without installing software, provided the site accepts the specific OFF variant and produces the required FCStd structure. Verify the resulting document in FreeCAD because online conversion may preserve only geometry and may not expose the same mesh-to-shape controls as the desktop workflow.

Quality and compatibility limitations

OFF commonly contains only vertices and faces, so it does not provide FreeCAD feature history, sketches, constraints, parametric dimensions, material definitions, or reliable units. The converted FCStd therefore cannot normally be edited like a model built with Part Design.

Creating a solid from a mesh requires a suitable closed, consistently oriented manifold. Open boundaries, duplicate vertices, inverted normals, self-intersections, and non-manifold edges can produce an invalid or incomplete shape. Repair the mesh in FreeCAD's Mesh tools or another desktop mesh editor before creating the shape.

Large or highly detailed OFF meshes can create very large FCStd files and slow boolean operations. Preserve the original OFF file as an archival source, and use a reduced mesh only when lower polygon density is acceptable.