Hi @Ian,
based on what you describe there…
…and the pictures you posted, I think there are a few things you should consider.
For 3D printing and visualization you really do not need Nurbs at all. So any SubD/mesh workflow will work for you just fine. Fighting with fillets for anything that are not extract mechanical parts of your model seems like a losing battle.
A very effective workflow is creating all the organic shapes in SubD, and then adding mechanical details in Nurbs (things like cylinders, flat planes, etc.).
Also I think you might have found out that some of those engines, since they were build from pattern masters (probably build by hand in wood/wax/plaster/etc) by hand they are not as precise as what you would do today in a CAD to CNC/3D printing workflow. Except probably for round shapes turned in a lathe.
SubD retopology is an excellent way to build these macro forms, before you add details with booleans. Also 3D scanning is a very effective way to capture those castings original surfacing results, as compared to their theoretical intent in their drawings.
Here’s an example of a part that had no cad and how we scanned it an retopologized it. This was an experimental project at my company Fresco Design, so it’s not confidential or under NDA, so we can share it out (unlike most things we do).
- start with a physical sample (not different than your engines)
- 3D scan it, modern scanners can give you a really nice watertight model with a few passes. And all the stitching work is quite simple these days (if you have a beast PC of course)
- Retopologize by planning your poly layout, and your loop flow. This IMO is the most important part, and what probably dictates how easy/hard will be later on to add details as you need them. This is also what takes most practice and skill.
We do our retopo work in Modo. You can also use tools like the wonderful $100 Topogun, or Blender has some neat tools for this too. I read here today that @theoutside is planning to start bringing some retopo tools to Rhino too. Besdies proper retopo tools, I know the Rhino team loves to praise the QuadRemesh tool too, I do not find it of much used for these kind of controlled shaped like man-made mechanical objects like these. Even using its curve guides seems extremely stubborn IMO, but maybe you have better luck? If anything, it’s still a great tool to get you 40-50% there, especially if you are not fast at SubD modeling. In our case we prefer to layout the flow of polygons based on the form we have to tackle for retopology, or the form we have in our minds that we are designing while modeling.
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here’s a Symmetry comparison of input (3D scan) vs output (Retopo SubD)
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With tools such as blendshapes/morphmaps you can add topology based detail that you want to explore it’s gestural state. For example for these castings we wanted to be able to add more/less shutline lip, this is where all the imperfections of the casting go to, and then in a secondary process you remove them form the metal part. Similar than some of the parts I see in your photos. So if you were to cast these parts in medal, you will want to bring back to your model this geometric state that was removed by grinding.
Rhino does not have blend shapes yet, or ways to store control points positions AFAIK. I was hoping that Bongo 3 would support these. Blendshapes are extremely useful for design iteration and for compensation of manufacturing processions like warping or shrinking. But you can at least manage the two start and end states with duplicate models, a horrible hack I know. I’d never do it myself but I’m mentioning it because I know that many people prefer (or are limited) to use Rhino for everything, instead of using the right tool for each task.
Another reason for SubD: it’s extremely friendly for high end visualization work, where you have a lightweight model with sensible placement for seams to UV unwrap all textures (you are also better off leaving Rhino for that task at the moment), and then you can bake all the rendering detail into low poly models too for Web Visualizations and AR.
Here’s a rendering done in Rhino/ Octane after being UV unwrapped in Modo:
and an animation in Modo:
That kind of animation work can easily be done in Bongo too, but then you could only export still frames, not geometry to other platforms where you want that animation to go, like here in Sketchfab on any browser:
or here in AR right on yours space (look at that QR code with a modern phone and follow the link):
There’s one more think you slould consider to your workflow too, This upcoming gem from @DanielPiker:
I hope this helps, please let us know if you have any questions.
from my team, @IgorK and @jsantocono were involved in this project too.