Rhino 3DM .3dm
Rhino’s file format, built on the openly published OpenNURBS kit.
What a .3dm file holds
3DM is McNeel Rhino’s native format and, unusually for CAD, it is genuinely open: the OpenNURBS toolkit that reads and writes it has been published freely since the 1990s. It holds NURBS surfaces, curves and solids alongside layers, materials and the render meshes Rhino keeps for display. Those render meshes are what convert here; the underlying NURBS mathematics has no equivalent in a polygon format.
Commonly seen in: Rhino, Grasshopper, architecture, jewellery design, marine design.
| Data | Stored in 3DM |
|---|---|
| Geometry | Yes |
| Materials and colour | Yes |
| Texture maps | Yes |
| Animation and rigs | No |
| Scene hierarchy | Yes |
| Read here | Yes |
| Written here | No |
Tested against a real file
The last sweep loaded Rhino_Logo.3dm from three.js examples through the viewer on this site: 131,948 triangles across 12 meshes and 8 materials, in 4.0 seconds. Every format's result is on the test results page, run 2026-09-08.
Which way is up
3DM is a Z-up format, which most of the rest of 3D is not. Files are read exactly as written and stood up for you in the viewer; the converter has a switch for it, so a model does not arrive in the next program lying on its side.
Convert 3DM to another format
Every pairing has a page saying what survives the trip.
Other things to do with a .3dm file
Questions about 3DM
How do I open a .3dm file?
Drop it into the viewer on this site and it opens in the browser, with the scene tree, the materials and the mesh statistics. Nothing is uploaded. If you want it in another program instead, convert it to GLB, which almost everything reads.
Is 3DM a good format to archive in?
3DM stores geometry, materials and colour, texture maps, scene hierarchy. Anything outside that list will not be in the file at all, so archive the original alongside it if the surfacing or the rig matters.
Does converting 3DM lose quality?
Geometry is copied vertex for vertex, so the shape does not degrade. What gets lost is whatever the target format has no field for: convert to STL and the materials go, convert to OBJ and the animation goes. The comparison table on each converter page says exactly which.
Formats that hold the same things
Or go back to the full format reference.