Convert surfaces to dense meshes and export them

I have to say that I’m still using MoI3d export to export surfaces from Rhino to 3d print because I think it`s far better (edit: IMHO).

This is the max resolution that I can get from Rhino’s 42cm diameter sphere.

For sphere is ok but for complicated shapes, I lose my resolution and hard edges.

MoI3d in that case is much simpler to operate and I can reach many millions of polygons. I`ve exported even more than 6M polygons which can give me a nice smooth 3d print of large objects after later decimation.

This is not the maximum resolution. I can get in MoI3d much denser export:

Feature request: please allow converting surfaces to mesh and later export of multi-million meshes with tiny edges for large objects with large surfaces (same as I can do in MoI3d).

Edit: If I don`t use meshing correctly in Rhino then please let me know how to do it correctly to get deser final meshes.

Edit2: If I won’t convert my large objects (surfaces/subd) to extreme small edges (before decimation) then after print my objects looks like that:
This is an extreme example of how should not prepare rounded shapes for 3d printing purposes (it`s not smooth)

Yes, you maybe need to learn a bit more about Rhino’s mesh settings.

Even with my “standard” mesh settings, I get around 100K polys when meshing a 42cm sphere (as compared to the 33K in your image above). If I push the settings finer, I can get as many polys as I want - here ~1.5 million polys.

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Are you able to reach 6mln?

Edit: So maybe MoI3d isn`t better in that area only easier to understand (for me).

Edit2: Could you tell me which value in mesh settings will drive me to the highest possible poly counts (on that 42cm sphere)?

Have you made the slightest effort to understand Rhino’s mesh settings?

The premise of what you’re trying to do seems a bit absurd. No large scale printing technology is capable of doing anything with 5 out of those 6 million polygons, I don’t even get 500k polygons when I crank the mesh tolerance to 0.0001". It’s like there’s some other problem here that you think the solution is to try to choke the slicer instead of tuning the printer or the finishing process.

No, there does seem to be an artificial cap of around 1.6M polys on the sphere - that probably needs to be discussed with McNeel. Some of the settings look to be ignored when the mesh gets over that limit.

However, I don’t really understand the need - on the 42cm sphere the mesh facets are only around 0.8mm x 0.8mm at the equator. I have been 3D printing stuff for a long time and I have never felt limited by the number of polygons Rhino allows.

I`ve designed more than 80 parts for cars (bumpers, addons, splitters, spoilers, and side skirts.) and I was involved in printing them (slicing, settings preparation and sending to gcodes).

When I prepare parts for 3d printing they have many millions of polygons but after that, I do decimation over it to one single part for 3d would not have more than 900K polygons. That part is sliced to smaller ones. So I have experience with that. Maybe not in meshing in Rhino. So I decimate high poly counts to lower later. But with that my smallest features look better. I`ve checked that.

This is my 3d print after painting and molding (this is customer’s photo after his painting)


This is what I wanted to point out here. That in MoI3d I can reach every polycount number which comp can handle and I don`t have any CAP there.

I think that Zbrush has the best decimation engine. I import to Zbrush maximum poly count and do decimation there. After that smallest features, fillets etc. will look much better IMO. The side skirt has about 2.5m and it could have really small features which would look better if you would export it with a higher polycount.

The second way would be to do more smarter mesher which would work like a Zbrush decimation master.

So in other words high poly count for 3d printing is not a finished product for me and I have to use decimation in Zbrush over that.

why not design with surfaces and solids and use export to stl? You can set the maximum distance between original surface and the polygon mesh very small for instance a 1/10K of a millimeter.
slicer programs use stl standard

That cap appears to be on only one smooth object. While it shouldn’t be there, if I make a more complex object, the cap is not there. I created a random object composed of spheres and boxes and I set the max edge length pretty small and set Rhino off to mesh it. It took several minutes and used 22Gb peak memory, the command line finally reported about 66 million polys. However, it seems to have crashed trying to finish… white screened and wouldn’t come back.

Asked it for something a little more reasonable in terms of max edge length and it created a mesh with about 5.5 million polys in a relatively short time.

And another try with an even smaller value yields 11 million polys.

I don’t quite understand this - decimation can’t really add detail where there is none to begin with… or?

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3D printing accuracy depends on the printer, print settings and slicer programs.
with FDM the layer heigth is very important for instance.

Thanks for the help. As I said before, I prefer meshing with Decimation Master and for that, I prefer having more high poly count to preserve details during decimation. After many tests, I`ve found that was best for my meshes.

Here nigh 3 million faces for simple sphere, that is even smaller than what you have (21mm radius) in Rhino 7.

Mesh settings

Along the same method it is easy to get say 7,5 million polys for the same sphere

This probably is going to be limited by available RAM.

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And, in reference to the images of the real parts you posted above, if you are splitting them into printer-sized parts, 3D printing them and then re-assembling, you are going to need to glue/fill the joints, sand the whole thing, then prime and paint it. Any very small detail will be lost in the process.

There isn’t really a cap other than probably what the OS allows you to allocate for memory. On my M1 that appears to be around the 7,75 million for the sphere, but I wouldn’t be surprised if that number were higher on machines with more memory and more swap. Also note that in the case of this smooth sphere that is 7,75 million quads

Note that this is for the meshing operation. Rhino can hold more than 7,75 million in a document even on my M1, obviously.

It probably needs a long time to recover from adding the object to the document, no doubt lots of swapping between disk and RAM going on, which can be a very, very slow process, especially on slower drives and with slow bus speeds. If you bump your swap file size you probably can do even larger meshes, but it’d take even longer to get added to the document.

No, I’m talking about this:

42cmSphere.3dm (2.7 MB)

With the file above, try the following mesh settings - if the max edge length is set to anything less than about 1.3, I always get the same mesh - with 1592106 points and 1591272 polygons. So Rhino is not obeying my request - the edge length I get around the equator is about 0.8mm

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Yes, don’t refine the mesh and don’t use simple planes. Also set maximum aspect ratio to 1 (for nice squares) and density to 1. Maximum angle to something very low as well.

Neither of those actually help. Simple planes shouldn’t change anything because there are no planes in this object. Unchecking Refine Mesh actually makes less polys, not more. Rhino should obey my request and make a mesh that has facets with an edge length of no longer than 0.1mm. That’s what the setting is for…

As I said above: Zbrush decimation master is the best engine to get printable files IMHO. To give it the opportunity to give me the best smoothness and best detail I need to deliver their HQ mesh. It doesn`t mean that I need deliver there 100mln but a big bumper which is sliced into small parts has about 13-20 printable parts (per side because the bumper is mirrored). Every part is about 500-900K (sometimes less). 14* 500K = 7mln polygons (in total).

This is the interior part of my addon before slicing to printers (low scale production):

Well I would be interested in seeing if Rhino could do as good a job with the right combination of meshing settings without having to make a huge overly-dense mesh first and then decimate. To test we would need a sample surface part and the resulting final decimated mesh to compare to see if Rhino meshing could be made to work comparably.

But anyway, if you have a workflow that is working for you and is reliable, that’s already pretty good.

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To be fair I start to include Rhino more and more into my workflow. That specific bumper above is a pure subd which has been booleaned, thickened in polygons and then decimated. Now I`m doing mixed workflow where I started to use Rhino. In that mixed workflow, I used MoI3d to export the mesh. Now after your help I will be able to export meshes straight from Rhino to Zbrush. Thanks.

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