Rhino 7 Subdivs working in Rhino 6?

I’m new to Rhino SubDs (not to SubDs in general, though), so here’s a newbie question:
It is obviously possible to save a SubD object from Rhino 7 as a Rhino 6 file and open it there. The ‘What’ command even recognizes it as ‘SubD’ in R6, and it seems to be possible to edit it in the usual manner… face extrusions, component selection, … amazing!
How is that possible? Does R6 have SubD features already?

However, using SubDs would be perfect for a modelling job at hand, and I wonder if I should give it a shot in Rhino 7, hoping the pillars of the earth will not come crashing down on me, or go with R6, since it seems to work there anyway.
Best regards

How is that possible? Does R6 have SubD features already?

Yes, it has some limited version of them since the beginning that were mostly hidden commands used for testing, it existed more behind the scenes. R6 doesn’t have all the subD tools and editing capabilities. If you are thinking of fully incorporating subD into your workflow you will not want to be using R6, especially as they add new features to them in R7. (and they exist in Grasshopper in R7 also, but not in R6)

Understood, thank you!
Would it be a wise idea to work in R7 already you think? Like are there still plenty of bugs and traps with SubDs, or are they ‘there’ already?
Hard to say I know… Just the general feeling.

Hi, Eugen,

If you’re going to use Rhino SubD, then you need to use Rhino WIP (V7).
(The subd support in Rhino 6 was a test, it is out of date, it is buggy, and it will never be fixed.)

Rhino SubD is V7 is a major new feature. Every weekly release of the Rhino WIP contains important SubD fixes and improvements. For some people, it is useful in its current state while others are waiting for more features.


I jumped in and work with SubDs in R7 all day long now. No crashes yet.
The way they are implemented is pretty nice!
What I found until now:

  • Some tools convert the SubDs into polysurfaces automatically (slice e.g.). It’s not always clear that this is happening.
  • It’s not possible to convert polysrf to SubDs. Is this geometrically impossible, or just something not yet implemented?


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In general, converting polysurfaces with complex trimming to subs this is a hard problem that involves lots of approximation. For simple polysurfaces with no complex trimming and non-rational cubic surfaces, it is possible to get nicer results. This feature is on the long term to consider list, but there are many more important things we have to finish first. If it ever appears, it will be later in the Rhino 7 cycle or provided by a 3rd party plugin.

Just adding to what Dale just said…

When you run ToSubD, you are asked to select “meshes, surfaces, and extrusions”. If you had pre-selected a polysurface, that will be deselected and you are prompted for input. At that point, you can:

  • select a polysurface -> this will automatically trigger sub-object selection of the face that you clicked on
  • window-select the entire polysurface -> all sub-object faces will be selected

When you then finish the command, all selected faces of the polysurface will become individual SubD objects. If - and only if - the input polysurface was a very simple one without any trimming, you can simply join all SubD objects into a single object.

Would you expect something to happen?

In Rhino WIP, try QuadRemesh. It has a SubD out option and will take a polysurface as input. It some cases you might get something useful.

In other case, like this, you won’t likely get anything useful.

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Pro Tip

There is a reason that accountants shouldn’t use Rhino.


I read this to mean that there should be some indication to the user the it’s happening so he/she can keep their mental model of the Rhino model’s state up to date. Can’t leave the user dazed and confused and still have them love your tool.

Thanks everybody for the tips!!

Good question… an indicator that the SubD got converted to PolySrf is that the selected object suddenly displays lots of isolines.
Actually, that should do. A popup warning would be super annoying (like the history break is - turned that off), so no good idea.
Maybe a heads-up display of the selected object’s type? But what when there are 1000 different objects selected… Dunno.

A question regarding backwards compatibility:
If I just load SubDs into Rhino6 and never edit or touch it, can I rest assured that it will ‘hold’?
Or was the SubD data model extendet/changed in R7, so some models will import, others not?

Asking because at the time being I’d like to use R6 because of plugins, but still enjoy DubDs already.

That’s what I read as well.

Hence my question. I don’t know either.

What will it take for you to still love the tool, Al?
The Properties panel shows the type of object that is selected. Perhaps that’s not clear enough? Messing with the isocurve display will likely have some people react furiously. We can probably add rapidly blinking lights somewhere. Any preferences towards color and frequency?

More stupid suggestions to indicate the object type:

  • Color code in the selection? Shades of yellow or whatever is chosen? But then every other object should have a color of it’s own, too, and that’s a bit much.
  • A brief warning in the command line: “converted to polysrf”? Might evade the eye too easily.

Or maybe just stick to the fact that isolines show up.

But that wouldn’t work in every display mode (I would hope).

You can change the display properties for SubD objects in the display modes that you use (custom or default) and you should already be able to get them to display differently enough if you really need a type of identification.

Not all features of WIP SubDs are supported in 6. I’m pretty sure that creases don’t transfer.

They do, actually! Just seeing this.

… Huh. So they do! Must be misremembering. Thanks for the heads up!