I have an STL file from Thingiverse that needs to be edited. There is plenty of software to convert STL to solids, however, MOI is the preferred software. Does MOI require an STL file converted to another format before importing into MOI? Is there an easy method to edit a file and avoid reconstruction of the file point by point?
The STL file is for 3D printed parts.
Hi Tim, STL format is generally not suitable for import into a CAD program like MoI.
STL format was not designed as a way to transfer design data at all, it's just a dump of triangles that was only ever meant to be consumed by the print slicer and not edited.
So it's not an easy process to do that, the data that you have is just fundamentally not the kind of data that MoI is set up to work on.
But I don't recommend trying to do that - CAD models do not work well when having something like hundreds of thousands of little trimmed planes in them.
For STL editing you would be better off loading it into a polygon modeling program where at least the data matches what the program is designed to work on.
In a CAD program there is some overhead for each face, like there are 3D edge curves and also 2D edge curves in the parameter space of the surface. This allows to have an accurate model where something like a sphere is represented with just one precise surface but it's not an efficient way to store a hundred thousand triangles.
One method you could use for getting some data to begin the rebuilding process is to get it converted into .obj format and then use the OBJ to 3DM wireframe converter from here: http://moi3d.com/resources#Obj23dmWireframe_converter which can convert polygons in an .obj file into wireframe line segments in a .3dm file and you can then open up that wireframe in MoI.
You did not post the specific STL file that you wanted to convert to a "Nurbs solid".
I used a fairly simple STL for a mount for a 3M respirator cartridge, HEPA + Organic, filter + activated carbon, to a fan. (About 155 kb)
(The STL imported to MoI would be about 75,000 kb, a huge amout of overhead.)
It is just a flat slab (2 planar slab surfaces) with a few round holes, plus a cylindrical "nipple" for the cartridge.
Imported the STL to MeshLab, and saved as .OBJ.
Used ImportOBJ script to get the .OBJ file into MoI. (Did not try the OBJtoEDM script.) (About 450 kb) It is a large number of triangular faces with edges, mostly planar.
Then did a couple of hundred or so of MoI geometry commands to (begin to) get a NURBS solid. (Did not finish) It was a lot of work...
It might be easier to just start from scratch, or trace outline images...
It would have been helpful to have a script to get the perimeter of a planar mesh of triangular surface (edges).
This would not help for a 3D "dolphin" mesh.
There is a tool but I never had chance to used it, is tool you can buy via contact, and it's maybe for a developers, because I think is more like to the C3D kernel, but I'm not sure. https://c3dlabs.com/en/products/c3d-toolkit/b-shaper/
Anyway here some examples:
If the object is simple you can rebuild with many tools like FreeCAD.
I could not find a price for C3D B-Shaper, but a companion module showed $1000 per month, so I am sure that the program is way beyond my budget.
There are a few sites explaining some of the mathematical type steps used for the conversion to b-rep, (Segmentation, Normals, Curvatures...). It is not an exact science...
Also the program appears to be RU.
