Dealing with meshes

Hi all,

I have a very intricate mesh file that I would like to import to Rhino and eventually turn them into nurbs so it can be edited. Picuturing a car with all the detail parts in it. Even screws. I think the file was originally created in. 3dmax. LOD is the maximum I have every seen.

What’s the best practice to clean up these meshes? My limited knowledge is telling me to get it in WIP and turn meshes to nurbs and down save it in R6 so I can edit it.

Once I did that, the file grew to 1.5G. My ways of making it lighter is to split the parts into blocks and link them back to the master assembly file. I am able to downsize it to 990m by doing so but the file is still working very slow and it crashes a lot.

What would you suggest to move forward? Did I mess up the meshes-to-nurbs process at the beginning so that’s why it keeps crushing on me?

Thank you all in advance

I’ve done things like this before - it would help to know what you mean by “edit” the surfaces to better answer - are you talking about restyling it? Or maybe just minor stuff like assigning materials and maybe adding or deleting details?

By edit I meant minor trimming and scaling not even texturing. Possibly rebuild some of the polysurfaces to simplify it. If there is anything too complicated. May delete it and patch holes. These sort of stuff.

Thank you

So in that case, it’s probably best to do all that in a software that plays nicely with meshes, instead of trying to wrestle with in in Rhino. Each FACE of those meshes gets converted into its own surface - so when you convert a mesh to NURBS in Rhino, you very quickly end up with polysurfaces made up of thousands of individual surfaces. You can’t even really rebuild a polysurface using the Rhino Rebuild command - so there’s not easy way to take those thousands of surfaces making up your polysurface and turn them into something coherent and editable. You may be able to trim and scale the meshes themselves in Rhino - sometimes that works, sometimes Rhino can be very buggy with meshes. That in fact would be my primary suggestion - try using the mesh edit tools in Rhino, and of course you can scale them and move them around all day long no problem. If you want to do anything more complicated than that, then you essentially need to treat the mesh object the same way you would laser scanned data - you’d use it as a reference to build your own surfaces on top of that mesh, but you’d never want to actually directly use the mesh. TLDR - MeshtoNURB is a dead end, try finding other ways to achieve your goal.

I see. Eventually I want to cut it with clipping planes and layout the sections as documentation with dims and annotations. Thats why nurbs is still the best bet. I do plan to use the meshes, now the polysurfaces, as references and build the surface in rhino so they are just the stand-ins. Base on your point, I may have better luck with meshes itselves due to the lighter file size. My initial reason to turn meshes to nurbs is that the OG meshes are hard to group or even organize. Now I have the polysurfaces layered and organized. Maybe I can turn it back to low poly meshes and use those meshes as tracing elements. Does that sound like a stupid idea? Thank you so much for your input.

I think using the meshes as the reference for rebuilding is WAY better! Like, you can project curves onto meshes no problem, then you can rebuild those curves. Make your surfaces from those. Lather, rinse, repeat. You can even create polylines by tracing vertices on your meshes, then convert those to curves. For something like that I use Curve - Free Form - Fit To Polyline and then use the Interp setting - this way your curve will pass through your vertex points. I’d then take THAT result and rebuild it, because Interp Curves tend to be overly dense imho. If you want to get crazy with it, you can use PointDeviation to see how close your NURBS surface is to your mesh. PointDeviation will accept a mesh - any mesh, laser scanned data, obj stuff, heck render meshes extracted from Rhino - as a valid input, and then you can see how close your NURBS surface is to each vertex in your mesh. If you are lucky enough to have a copy of VSR that’s the ultimate tool for this, but it’s no longer sold and only works on V5. That being said, there’s a way forward with standard Rhino tools on a mesh. Only use those polysurfaces as an absolute last resort I’d say.

This was done with the aid of VSR, but in the way I describe - using the mesh as a rebuild reference, never going the MeshtoNURB route. Essentially one giant reverse engineering job, with an obj mesh as the reference instead of laser scanned data. Time consuming, but possible!

Just FYI here, Reverse Engineering like this is absolutely the most painful, un-fun job in all of CAD-dom. There is no trick–you need to know all of the tricks. There’s been a guy on here who’s been reverse-engineering a plane(planes are easier than cars, NURBS were literally created to make airplanes)for what feels like the last 15 years. It’s like what are you actually trying to do, is there any real need for this step at all before you get in way over your head?

I mean, I actually think this stuff IS fun, but maybe after a few car projects and a dozen or so full sized aircraft it’s really just Stockholm Syndrome? :rofl: :rofl: :rofl:

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quadremesh the primary surfaces in v7 and output as subd, then use the tonurbs command.

it vastly improves the reverse engineering process but does not entirely remove the tedium.