3dm

3dm is the native file format used by Rhinoceros 3D (Rhino), the 3D modeling software developed by McNeel. The .3dm archive stores the data needed to recreate a Rhino model, including precise NURBS geometry (curves and surfaces), polygon meshes, points, and annotation objects, as well as blocks and instance references.

In addition to geometry, a 3DM file carries modeling attributes such as layer structure, object color and linetype, material indices, and render settings. It can store construction history in some Rhino workflows, allowing edits to propagate through dependent objects. Topology data, such as Brep (boundary representation) topology and trimming curves, is maintained to preserve accurate geometry for modeling and manufacturing.

The format is developed by McNeel and is the native exchange format used by Rhino. OpenNURBS, an open-source toolkit provided by McNeel, offers read and write access to 3DM files, enabling developers to build interoperability with other software. The format is primarily binary, with versioning to accommodate new features and data types over time; newer Rhino releases add improved support for materials, textures, and metadata.

3DM has become a common interchange format in architecture, product design, engineering, and visualization, facilitating data transfer between Rhino and CAD/CAM tools, rendering packages, and 3D printers. While some non-Rhino software can read 3DM directly, compatibility is often achieved via the OpenNURBS library or by exporting to other standard formats.