Free online OFF to IGS converter

OFF files are commonly delivered as polygon meshes, while many CAD and engineering programs require the IGES/IGS exchange format. Converting them is useful when a mesh must be opened in an older CAD system, exchanged with an engineering workflow, or exported as a CAD-readable model.

What the OFF format is

OFF, or Object File Format, is a plain-text format for polygonal 3D geometry. It normally stores a vertex count, face count, vertex coordinates, and polygon indices; some variants also include colors or other attributes.

Mesh-processing and geometry programs such as Geomview, MeshLab, and custom research software create or use OFF files. You may encounter OFF when downloading scanned objects, academic test models, polygon datasets, or output from computational-geometry tools.

What the IGS format is

IGS is the usual filename extension for IGES, the Initial Graphics Exchange Specification. It is an ASCII CAD exchange format used by mechanical-design, manufacturing, inspection, and legacy engineering applications.

IGES can represent wireframes, surfaces, and some solid-model entities, making it more suitable than OFF for CAD systems that do not read polygon meshes. The conversion does not automatically turn a faceted mesh into clean parametric or smoothly fitted CAD surfaces.

How to actually convert OFF to IGS

Using 101convert.com

1. Open 101convert.com and select the OFF-to-IGS conversion.
2. Upload the .off file.
3. Start the conversion, then download the generated .igs file when processing finishes.

This option requires no installed software and is available free on the site. Check the result in the target CAD program because support for polygon-derived IGES entities varies.

Using FreeCAD

1. Install FreeCAD and open the Mesh workbench.
2. Use File → Open or File → Import to load the .off file. If the OFF file is not accepted, open it in MeshLab and save it as .stl or .obj, then import that file into FreeCAD.
3. Select the imported mesh in the model tree and switch to the Part workbench.
4. Choose Part → Create shape from mesh. Set a suitable sewing tolerance; a value that is too small leaves gaps, while a value that is too large can merge nearby details.
5. Select the resulting Part shape, then use File → Export and choose the IGES format, producing a file such as model.igs.
6. Open the exported file in the destination CAD application and inspect edges, holes, normals, and units.

Quality and compatibility limitations

A direct mesh-to-IGES conversion usually creates many triangular planar faces. It does not recover the original design history, sketches, feature parameters, analytic cylinders, or smooth NURBS surfaces. Large or highly detailed OFF meshes can also create very large IGES files and may exceed the target program’s face or memory limits.

OFF files generally do not contain reliable unit metadata; confirm whether coordinates represent millimeters, inches, or another unit before export. Vertex colors, textures, materials, and mesh-specific attributes normally do not survive in IGES. For manufacturing-quality output, use the converted model only as reference and rebuild or reverse-engineer the required surfaces in a CAD system.