What is a 3DM file?
.3dm is the native file format of Rhinoceros (Rhino), McNeel's NURBS
modeller used in industrial design, jewellery, architecture and marine work.
The format is documented and implemented by McNeel's open-source openNURBS
toolkit. A 3DM file can hold NURBS curves and surfaces, polysurfaces (Breps),
extrusions, SubD objects, meshes, blocks, layers, materials and annotations.
Sharing a 3DM with someone who does not own Rhino is a common headache: most general 3D viewers do not open it at all, and Rhino's own viewer options require installing software.
How Mes3D reads 3DM
Mes3D uses rhino3dm, McNeel's WebAssembly build of openNURBS, the first
time you open a .3dm file (about 2.7 MB, downloaded once). It then collects
everything that can be drawn as triangles:
| Object type | What is shown |
|---|---|
| Mesh | The mesh itself |
| Polysurface / Brep, Extrusion | The render meshes Rhino cached in the file |
| SubD | A mesh generated from the subdivided control net |
| Block instance | The block's geometry, at every placement, nested blocks included |
| Curves, points, annotations, lights | Not shown (nothing to draw as a surface) |
The model's unit system is converted to millimetres when it is set in the file, and object or layer colours are applied in the Original view.
The render-mesh catch
Rhino stores NURBS geometry exactly, and keeps a triangulated render mesh next to it for display. Mes3D, like most lightweight viewers, draws that cached mesh. Two ways of saving leave it out:
- SaveSmall (or "Save small" in the save options) deliberately strips render meshes to shrink the file;
- some scripts and exporters write geometry without ever shading it.
If a polysurface you expect is missing, open the file in Rhino, switch a viewport to Shaded or Rendered so meshes are created, and save normally. For files you plan to share widely, exporting a copy as STEP (for engineers) or STL/3MF (for printing) is still the most portable choice — Mes3D opens those too.
How to open a 3DM file here
- Drag the
.3dmfile onto the drop zone above, or click Choose 3D file. - Rotate, zoom and pan; use preset views and orthographic projection for straight-on views.
- Choose Original as the model colour to see object and layer colours.
- On a computer, measure point-to-point distances in millimetres, read the overall dimensions, and open the analysis panel for volume, surface area and estimated weight — useful for jewellery and casting estimates.
Who this is for
- Clients and reviewers who receive a
.3dmand just need to look at it. - Jewellers and makers checking a model's size and volume before casting or printing.
- Teams where only the designer has a Rhino licence.
On a phone
A 3DM sent by email can be opened in a mobile browser here for viewing and dimensions. The Mes3D app for iPhone, iPad and Android opens 3DM files from Files or Mail and adds measuring, mesh analysis and cross-sections, and can export the result as STL, OBJ or 3MF.
Limits
- Up to 200 MB per file in the browser.
- NURBS surfaces without cached render meshes are not displayed (see above).
- Materials are shown as display colours; Rhino render materials, textures and lighting are not reproduced.