3dm format and file size

My drives get filled quickly with all Rhino files. It feels like my 3dm files easily get very large. And often more so than they need to be (?)

Just as an example, the latest file I was working on is 32MB (which admittedly isn’t particularly large), I then made a RAR archive from it, and it only takes up 32.95MB. That is a significant size reduction and I can’t think of many other formats that I can compress to almost 10% of its original size…

I’ve also noticed that if I export a part as a STEP214, the file size becomes much smaller than if I exported it in the native Rhino 8 format. As an example, I exported a part just now and this is how much space it takes up

  • STP | 545KB
  • 3DM | 1283KB ( 235% larger )
  • 3DM archived as RAR - 521KB
  • STP archived as RAR - 98KB

So 2.3 times larger, and I’m curious of the reason for this.
Is there really that much information in the 3dm file that’s missing in the step?
Or is it just that it’s less optimized?

To me, it seems that perhaps the file managing in Rhino can be improved quite a bit
But then again, maybe I’m missing something fundamental.

Hello- please check SaveSmall - does that make the difference?


Completely forgot that SaveSmall was a thing, thanks.
SaveSmall gave the exported part a size of 545KB, exactly same as the STP
and the 32MB document is now 23MB instead

So there is definitely some improvement there. Any reason not to use this all the time?

Perhaps the render meshes already exist in some cache somewhere(?) or the document just isn’t that complicated, but there is no difference at all for me how long it takes to open the SaveSmall document and the original one.

So it seems like a win :slight_smile: I’m guessing it could be improved upon even more somehow?

Hello- mainly to avoid taking the time to regenerate the display meshes when the file is opened.


The Rhino format is not optimized to be as small as possible–obviously it’s not just “zipping” everything up internally–which is itself only one aspect of “performance.” It’s meant to be “robust.”