Rhino 6 - T splines - Z Brush Problem

@Paul_Bundarin I was working on a Rhino to zBrush workflow about a year ago. I will look back for any info. I was using T-Splines as well, but the OBJ file I exported from Rhino was after the T-Splines had been converted to NURBS. The OBJ from zBrush can be imported back into Rhino no problem, if I remember correctly.


Well, all people mean something else when talking about complex.

What can’t get done is taking a Zbrush mesh with millions of faces and convert it straight to Nurbs. None
of the people you know does that. Tsplines or any other converter will just freeze and you will have to
kill the application.

Obviously one can still use Zbrush and Rhino together nicely. If one really needs to convert the Zbrush mesh to Nurbs one had to stick to far lower resolutions – and as Wim stated the V6 converter should do (SubDFromMesh).

But you could also load a very heavy Zbrush mesh and simply keep it as a mesh. Converting to Nurbs doesn’t make it any better / more valid / more precise. You still may combine your Zbrush source object with some Nurbs geometry. The final product will likely end as a mesh anyway, for wax printing or similar, no?

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@hifred With all my searching I have learned that T-splines is no longer available and Clayoo is now a subscription product.
So you think the SubDFromMesh will accomplish the same transition if I work in a lower resolution? Will I be able to do the reverse and convert nurbs to subD then bring it to Zbrush? I’m wondering if that will suite me or will I still need an organic modeling program like T-splines? I won’t consider subscription programs.
I also feel that I have more options for editing an object in Nurbs format.

@Paul_Bundarin I do not think that is correct…but I have been wrong before. Clayoo can be purchased as a stand alone license AFAIK. I don think any of TDM`s products are subscription based.

The 1 year subscription mentioned on their website is to their premium level support/education products.

12 pm27 pm

Hey Paul,

You’re getting in deep when exploring transferring Zbrush files into anything else and any solution is inevitably going to be complex.

I’m an industrial designer and I often work between Zbrush, Solidworks and Rhino for highly accurate CAD work, mixing accurate data and the inevitably less accurate Zbrush work. The problem arises when bringing Xbrush files out of it and into anything else, as Zbrush functions at higher resolution levels that any other program I’ve ever used (or heard of!!!). This becomes a problem for other applications as they don’t have anywhere near the processing power to handle all the polygons.

In exploring a Rhino-Zbrush workflow I’ve realised that I’ll never be able to work with a Zbrush surface in any other program effectively, so this is how I work around it:

  1. I decimate my Ztool heavily (I mean 1-5% of the original polycount) and then export to obj (I don’t want details, I just need overall forms to help me model later.
  2. Import the obj into Rhino
  3. Make sure that Osnap “vertex” checkbox is on down the bottom of the window, this allows me to snap to mesh geometry without converting to nurbs.
  4. Model what I need in Rhino
  5. Export to OBJ from of Rhino at really high resolution.
  6. Import into Zbrush and use the decimated original body to line everything up.
  7. cut/combine/project details from imported Rhino model onto your Zbrush model. Dynamesh will be your friend!! If you’re not familiar with it, there are lot of good tutorials out there.

Unfortunately any solution going between Nurbs anything and Polygon anything is a very imprecise (and totally manual) art. It’s more trial and error than any real method.

Hope some of that helps!


this may be interesting

bye Riccardo

@sochin Is this price from the CAD Jewelry School? Have you purchased anything from them?

Are you working with Clayoo? Do you think it’s the best substitute for T Splines?


Well, SubD is new and not even officially available inside Rhino.The included converter still is in extremely raw state. It essentially replaces every single face in the SubD-cage with a Nurbs surface. More mature converters such as Tsplines try to create a usable patch-layout but no product outputs good Nurbs models in the sense that one may perform demanding surfacing operations on the converted model. If the goal is to cut some holes and possibly to create some simple fillets here and there this will do though.

This is the Zbrush sample dog converted to Nurbs with the V6 converter and with a precise hole cut into its belly. You can try this out right now by loading a quad mesh to the Rhino 6 Beta. Run the SubDFromMesh command, followed by the ToNurbs command.

If that all sounds too raw for you may use Autodesk Fusion for Nurbs conversion but that is a subscription program.There’s quite a bunch of other Mechanical CAD and dedicated Reverse Engineering programs which let you convert quad-meshes to Nurbs but they are very expensive + a lot of of them are subscription based these days. None creates a Nurbs model which allows for advanced modifications.

I can’t speak for McNeel but I dare saying No.
There’s no program which lets you freely convert models back and forth between SubD-meshes and Nurbs.
Rhino 6 won’t let you do this either.

Good news is that you can sculpt any Rhino model inside Zbrush. With Rhino 5, today.

I think you are mixing up techniques and terminology here. A SubD cage is a mesh with a particular topology with just four sided faces. Not all models with just quadrangles are SubD-Caged though. Meshes with such topology are ideal for smooth subdivision. But Zbrush will work just fine with any sort of less regular meshes as well. If the input is really bad there’s great ways for remeshing. If you want to bring the modified model back to Rhino you may simply re-import (I usually have no problem with the full resolution data and rarely have to use decimation). If you really need a Nurbs conversion you can create a conform mesh inside Zbrush.

@nic.kuipers Thanks for the info. I was assuming I would have to convert to a low res to be able to get into Rhino. I guess that would be trial and error to get the most detail possible. When you import to Rhino to work on it are you editing meshes in Rhino? What about converting to nurbs for better editing possibilities?

Do you have 2 versions of the object? I’m a little confused.

Apparently, SpaceClaim seems to claim that they do. Does anybody here have any real-world experience with that? @DanBayn?

Was The dog originally made in Z Brush? It looks pretty good to me. Do T-Splines and Clayoo work in subD quadrangles?
I have been under the impression that in order to do good editing I would have to have a nurbs surface to work with.

What kind of file are you re-importing? > Blockquote
Would having an inbetween program like Clayoo help with the transition? I’m assuming Clayoo is also quadrangles?

Hi Wim,
the clip on the page you linked shows a purely Nurbs based Reverse Engineering process.
There’s no Subdivision Surfaces modelling whatsoever involved.

In fact there are some CAD programs, such as Autodesk Fusion which allow for a limited back and forth conversion between Nurbs and SubD-Cage. Fusion stores the editing history – after applying some Nurbs features one may go back to the Control cage and deform it. When done the pre-existing parametric features get re-applied.

It is one of the sample models which ship with Zbrush.

That is a very broad statement.
Skilled modellers may produce very accurate models by Nurbs Surface modelling, that’s true.Less precise geometry representations on the other may be more inviting for quick design iterations. Sculpting programs like Zbrush allow for a sort of geometric complexity which can’t be achieved by any other 3D modelling process.

This guy creates and manufactures his jewelery only in Zbrush. No Nurbs conversion involved.
These baroque and roccoco furniture are modelled in Blender, also as a mesh.

Stuff like that would be a bloddy nightmare with Nurbs (not just in Rhino) So good editing depends.

An .obj works just fine.

As @hifred mentions, you may not need a nurbs surface at all. This really depends on your intent and manufacturing method.

I don’t have experience with any poly to nurbs converter that will give editable nurbs curves from an organic object by an automatic method. I recently saw video of a Rhino plugin, Surface2Mesh that looks like it may have a faster method of generating the curves than doing it manually. Maybe someone here has used it.

PowerSurfacing RE (for SolidWorks, no Rhino version yet, The stand alone version is Cyborg3D.) can extract a subd control cage from a mesh to create a nurbs surface. Then the nurbs surface can be snapped back to the original mesh (not the subd) to preserve the finer details.

The nurbs surface produced by T-Splines, Power Surfacing, and I believe Clayoo as well from an organic object can only be edited with the specific application. The export is a dumb solid, which is the same as the result from a more expensive solution like Geomagic Wrap/Design X.

For those interested, I have just completed a project with this workflow :

TSplines - Zbrush - Tsplines - convert to Nurbs

From this experience, I can truly say that when the correct approach is taken and the correct process order is worked out, one can get very very clean ordered meshes from Zbrush which can be converted to TSplines. The resultant TSplines being all quads, and incredibly evenly distributed.

Happy to share the process in Zbrush if anyone is interested…but the project hasn’t been released to the public as of yet.

Resultant surfaces were to be 6 axis milled from hardwood a using Kuka robot.

Absolutely interested.

// Rolf

Hey @rupertenberg

That’s pretty cool and might be in the right direction! Do you mind sharing a bit more info?
I’m assuming talking in Tsplines you’re either using an old Rhino or Autodesk Fusion?

@Paul_Bundarin In terms of editing meshes or converting to NURBS it doesn’t really matter to me. I often leave it in meshes, because the amount of information and edit/osnap points gets out of control real quick after it’s converted.

And yeah, you’ll end up with two versions of your model + the new geometry when you import back into Zbrush. What you need to do is keep your original Ztool open, then import the new geometry file. Then append the new Ztool to the original. If it all works out everything should be in the right spot at the right scale, but inevitably it’s off on the wrong axis or scale. What I meant was to use the body that you used as a guide in Rhino to help line up the new geometry when you’re scaling and moving it to fit so that everything is in the right spot. If you don’t need to be perfectly accurate to the last 100th of a mm then this is a good process, but if you do, then don’t take it back into Zbrush, just work from that point on in Rhino.

If you haven’t checked them out, boolean tools and Dynamesh for Zbrush can probably achieve what you’re looking to do without the complex surfacing or the high accuracy of Rhino.


Essentially I am using T-Splines to set up the geometry; Why? Because Rhino and TSplines are my strength…and…the accuracy required. After creating a TSplines base mesh I will then export as OBJ to ZBrush.
ZBrush is where it gets a little difficult. All the re-topology options, Dynamesh, ZRemesher etc. There was a hell of a lot of trial and error and writing settings down so in order to repeat steps. But, once the mesh had been re-meshed I then used the ZModeller brush to further refine the design. Bear in mind, this ZBrush step was primarily for aesthetic resolution and if required, the addition of organic detail.
Once the topology, density and aesthetic had been finalised I then exported as OBJ again to Rhino.
Conversion of the OBJ into TSplines again allowed me to accurately (.01mm approx tolerance) finalised some geometry before converting to NURBS. From this stage standard Rhino nurbs commands were used such as cap, fillet, boolean functions etc.

@Paul_Bundarin Not sure what price was from where as I just took screen shots from the TDM site and CAD Jewellery…I purchased Rhino and Rhino Gold from CAD Jewellery School when I started CAD as they are an Australian based reseller.

I have been using an Asiga printer for about 4 years and always liked the look of Mark Kuhlein`s Solus printer

As it turned out when my Asiga died recently I purchased a Solus from CAD Jewellery School as they are a reseller. So I have spent heaps of money with them with no problems. Rik is a good guy…he helped me out when TDM told me my license did not belong to me after I needed to re install RG after an install of an early Clayoo2 trial trashed my system. So glad I purchased through a reseller as TDM`s records got stuffed up and they were certain I did not own my serial number and would not let me reinstall RG until Rik proved my purchase.

Unpaid plug for the Solus, half the price of the Asiga, twice as fast, better quality prints and the support and community are out of this world. Some of the work Universities are doing with it are very impressive.

Back to Clayoo…I think I was one of the very few people that used Clayoo1 extensively. I was certainly one of the only ones that were active on the old message boards.

I gave up on Clayoo1 a couple of years ago after waiting on promises and promises. I have no idea how good Clayoo2 is but it will come with Rhino Emboss and a sculpting feature. You can read my comments on Clayoo 1 in this thread from back in 2016.

You might also find @gustojunk comments of interest after I think he tried Clayoo2.

So I have experience with TDM but not much of fan anymore sad to say. Was a very different company when I first started CAD and Rafael was always on the boards. I would use t-SPlines via Fusion before I would spend more money with TDM/Stuller until I see someone with far more experience than me like @gustojunk say the product is good…which he did not.

I’d like to thank everyone for sharing their knowledge and advice to this topic.