Convert Rhino 6 to Rhino 4
Rhino 4 (released 2007) can't read files saved by Rhino 6 (2018) — a 2-version gap in the OpenNURBS archive format. This tool rewrites your .3dm from v60 down to v40 in seconds, translating newer object types to their Rhino 4-native equivalents.
Files will be converted to Rhino 4 (if compatible).
Why convert Rhino 6 files to Rhino 4?
You're modeling in Rhino 6 but need to hand the file to someone on Rhino 4 — a client, subcontractor, university lab, or team member who hasn't upgraded. Rhino 4 is still used by archived project files, older marine and jewelry workflows, and Rhino 6 is used by long-running architecture projects, jewelry studios on stable licenses. Rather than asking them to upgrade or waiting for a re-export, convert the file here and send them a Rhino 4-native .3dm.
- Open Rhino 6 files in Rhino 4 without upgrading your license
- Official OpenNURBS 60 → 40 write pipeline
- NURBS surfaces, curves, meshes, layers and blocks preserved
- Runs in seconds, right in your browser — files stay private
- No plugins or software installation required
- Works on Windows, macOS and Linux
How it works
- 1
Upload your Rhino 6 .3dm file (drag & drop or browse)
- 2
We detect the file version instantly from the file header
- 3
Click Convert — the file is rewritten in Rhino 4 format using the official OpenNURBS libraries
- 4
The converted file downloads automatically
What actually changes between Rhino 6 and Rhino 4
Features introduced between Rhino 4 and Rhino 6 are downgraded to their closest Rhino 4 equivalent: 64-bit-only object flags, Gumball transforms, modern surface analysis data, embedded Grasshopper 1 definitions, revised block manager metadata, new render pipeline data, and updated annotation styles.
The archive header is rewritten from OpenNURBS v60 (Rhino 6) to v40 (Rhino 4) so Rhino 4 recognises the file natively.
Rhino 6 (2018) to Rhino 4 (2007) is a 2-version step. Core geometry survives cleanly; a handful of newer object types get flattened to older equivalents.
Geometry preservation
NURBS surfaces, curves, meshes, layers, blocks and materials are preserved. 64-bit-only object flags, Gumball transforms, modern surface analysis data, embedded Grasshopper 1 definitions, revised block manager metadata, new render pipeline data, and updated annotation styles are the ones that need translation: they get replaced with the closest Rhino 4-native representation (e.g. SubD → mesh or NURBS, newer annotations → base annotation types).
Tips for a clean Rhino 6 → Rhino 4 conversion
- Save a copy of the original Rhino 6 file before downgrading — some newer features can't be perfectly round-tripped back.
- If you're on Rhino 4 yourself and just want to hand the file to Rhino 4 colleagues, this is a one-click job.
- Rhino 4 predates modern annotation styles. Add dimensions and text after conversion in Rhino 4 rather than trying to preserve Rhino 6 styles.
Rhino 6 to Rhino 4 — FAQ
Can Rhino 4 open Rhino 6 files?
No. Rhino 4 uses OpenNURBS archive v40 and can't parse files saved with Rhino 6's newer v60 archive. Converting the file to the Rhino 4 format with RhinoFileConverter solves this in seconds.
What actually changes when I convert Rhino 6 to Rhino 4?
The archive version is rewritten from v60 to v40, and features that didn't exist yet in Rhino 4 — 64-bit-only object flags, Gumball transforms, modern surface analysis data, embedded Grasshopper 1 definitions, revised block manager metadata, new render pipeline data, and updated annotation styles — are translated to their closest Rhino 4-native equivalent, exactly like Rhino's own "Save As Rhino 4".
Will my SubD or ShrinkWrap geometry survive from Rhino 6 to Rhino 4?
Rhino 4 predates SubD (added in Rhino 7). SubD objects are converted to a mesh or NURBS approximation on the way down. If you need editable NURBS geometry, run ToNURBS on SubDs in Rhino 6 before converting.
Is my file uploaded to a server?
No. The conversion runs entirely in your browser using the official OpenNURBS WebAssembly build. Your Rhino 6 model never leaves your computer.
Is there a file size limit?
Free conversions support .3dm files up to 25 MB. Paid plans raise the limit to 200 MB (single) and 250 MB (unlimited) — enough for most architecture and product-design files.