Subdivision Modeling

Hello All,

I have been a Rhino power user since 1999. Through other applications I would use subD modeling to get to a better results for my projects. When T-Splines was developed as a plugin a ways back I jumped on the opportunity and bought the plugin. Then Autodesk bought T-Splines and “fused” into Fusion 360 and dropped supporting the plugin for Rhino! Not good. So I have been continuing to use Rhino 5 with T-Splines as my main source for modeling. Well now here we are and the McNeel team, a million thanks!, has come full circle and developed sub D tools within RH6 + , more robustly, in WIP RH7! So my question is, I just bought a new workstation and upgraded to RH6 and also installed WIP RH7. What is the best way to access my RH5 files with T-Spline geometry via RH6 and 7? I have ever continuing projects that I need to efficiently open and continue to working in. Should I open my files in RH6 save off and then open in RH7? or can I cut to chase and open my RH5 files directly in RH7?

Any insight into these possible protocols would be much appreciated!

Thank you!


Have a look here:

Hi Rudolf, why would you have to open your RH5 files in RH6, save them as Rh6 files, then open in RH7? what benefit would that give you?

Keep in mind that opening your RH5 models with Tsplines geometry in either RH6 or RH7 will convert that geometry to Nurbs (not more editable as SubD).

You might be better off converting the SubD to Low poly in RH5 (I forgot if that’s a Tsplines option, or you have to export those objects as low-poly as OBJ and import back). Then your RH5 file would have Nurbns geometry + ‘Low Poly’ mesh geometry that you can open in RH7, and then convert all those ‘Low Poly’ objects _ToSuD.

That would be a really easy thing to script for someone I think, just sayin’. Even a Service Release from McNeel for RH5, that lets you export your models as V7 as editable native SUbD would be a low hanging fruit to get those people to upgrade. Maybe?


Not possible.
The V5 development infrastructure is long gone.

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aaah… John, we always start our negotiations with you saying absolutely not, never, impossible… and you know that many times things have not ended that way :wink:

…but this time, I’ll let you win it. I have better battles to pick.


I would take a look at this video. It can show how you might be able to make the the transition to Rhino 7 Subd tools:

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Please watch the video that Scott links. Kyle does a good job of showing that you can save your T-Splines in “box mode” and get a SubD in V7.


There will be no negotiations this time @gustojunk.
We will not resurrect the V5 development system in order to generate another service release.
If you understood more about the infrastructure of the development system you would understand better.

The Video that Scott linked is the path forward.

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Yes yes. I said it first. I conceded to your victory and your priorities, so I get a credit for another fix, some other time, in some other area.

Those are the rules.


Hello Scott,

This is exactly what I was looking for. Thank you so very much for providing this link to video. What a great leap forward with RH7!

Love Rhino!



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Tsplines data should open up as SubD data. There will be some rework to do as Tjoints are converted to regular SubD data, but it’s not awful.


How about going the other way? I’m trying to send a box mode subD mesh to V5, and I’m finding that every way I try I keep getting modified meshes.
Is there a way to preserve the box mode structure of the subD and bring that into V5 to work with it in TSplines? The reason I want to do this is to be able to use curvature analysis while I tweak it.

Hi Ernest -

You should be able to use ExtractControlPolygon on the SubD object and export that mesh as a Rhino 5 file.

Nice. Thanks Wim!

@Rudolf_Baltera I am still sitting in Rhino 5 with T-splines. Was wondering if there is anything that you miss from t-Splines that you cannot do in Rhino 6/7 subD?..or is there anything in Rhino subD that is an improvement on T-splines. Really interested to hear your thoughts if you have the time.


you need to quadremesh then export it as a quad based obj file into tsplines.

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grab the v7 trial and give it a try! I think you will be pleasantly surprised.

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Hello Sochin,

I was in the same situation you are in a few years ago. McNeel has covered all the t-splines abilities in R6 +7 minus some hotkeys. But you can update those in UI.


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I’ve been using T-Splines for years and adopted to SubD quite early. Rhino7 has a lot of really useful SubD features but I wouldn’t say all T-Splines features have been implemented.

I really miss the T-Splines selection tools, like grow and shrink and also the ability to select a face and modify the selection into vertices or edges.

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