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SoliForum - 3D Printing Community → 3D Modelling/Scanning/Design → Sculpting from stl
Do you know any sculpting program that allows import and editing of stl files or other formats (the point is that object was built in cad program). I really like functions given by e.g. Blender, but i prefer to design in programs that gives me precision like Autocad, Rhino, Sketchup. So what i would want to do is to create object in some cad program then export it to sculpting program for finishing operations. I couldn't import any of my files to Blender.
This question has been asked many times.
The problem with STLs is that they are not solid objects, they just an outer skin covering the object, a shell. As such, many programs cannot modify the the STL to any degree.
Yes, they can import it, you can resize it, and even make some basic modifications like cutting it. But you really can't change its geometry in any meaningful way.
For example MeshLab will take the STL and it can affect certain changes by teaking the surface, but if you wanted to put a hole in it, or cut a notch, you won't be able to do that.
Same goes for NetFabb. NetBaffis great for sizing, celaning and slplitting STLs, but if you needed to make more detailed changes, it can't.
AutoCad, SolidWorks, Parasolid, they will import the object, but can't usually do anything with them.
THis is why you are better off finding the original model, and working with it in the program that created it, or exporting it to another program, if there is such an export module available. STL is more or less the final export designed for printing
You can always translate the STL file to an OBJ (I use MeshLab for this) then bring that into a mesh editing program. I think zBrush will do this; seems Sculptris does this too. The only problem that you have is scaling. My program (Carrara) scales the model differently so I usually have to guess at the size when I plate the model. YMMV.
It would help to understand that there are a many different 3D model formats, but primarily they can be grouped into 3 types: Nurbs, Polygonal & Solids, and conversion between them is not always possible or practical.
Nurbs are Bezier curves that define a surface. Much in the same manner Adobe illustrator can use bezier curves for 2D drawings, programs like Maya, 3D Studio Max, Alias and Rhino use Nurbs for surface modeling. One thing to keep in mind is that Nurbs surfaces are always open (meaning they can't form an enclosed surface), which also means that by definition, they are non-manifold.
Polygonal surface models are what an STL is, it's similar to a Nurbs in that it's a surface model, but instead of smooth curves it's built from many flat polygons. The more polygons you have the smoother the surface will appear (from a distance), but a curve will never really be totally smooth. However, they are always closed. Blender, Sketchup, Lighwave 3D, Carrara they all handle polygonal models
Solids are exactly what the name implies. The objects are made up of solid geometric shapes. When you draw a cube, it's a solid, six sided object, made of 6 faces and 12 vertices, which means the object has "thickness". In contrast a Nurb Surface is just that, a surface without any thickness. Programs that use solid models are Autodesk Inventor, SolidWorks, Solid Edge and Creo
While converting a Nurbs to a polygonal mesh is usually pretty common, Converting a solid to a mesh is easy. But going from a mesh to a solid object is not. There are some specialized programs that can do this, with varying degrees of success, and some of the high end software like Solidworks will try to analyze and detect solid objects within a mesh, but unless the object is pretty simple, it doesn't really work well.
Pirvan,
I bow to your wisdom... BUT...
While it's true that conversions can be tricky, it's often the case that subdividing a closed mesh in order to add detail doesn't affect the manifold nature of the original mesh, unless you deliberately cut a hole into it. Unfortunately, it's all too easy to do if you don't understand the software you're using.
Polygon modelers, though, do not always create closed meshes; I've seen some non-manifold meshes created by new users who want to 3d print their objects. There are often intersecting triangles and single planar facets littering the object, and that can cause issues with slicing after export to STL. Still, for more organic shapes, I find polygonal modeling the best way to get more organic shapes that CAD modeling cannot do.
Programs like zBrush and Sculptris allow for the original mesh to be subdivided in order to add details (wrinkles, reliefs) without really affecting the manifold nature of the original. True, you can create annoying intersections by pushing/pulling the mesh too much, but that's the case with all polygonal editors.
I personally use Solidworks which will always generate a fully enclosed, manifold mesh. It's not very good for modeling organic , lifelike objects, but for mechanical design, it's awesome.
However, I also like to download and print models created with the likes of 3DS Max, Lightwave, or Maya, which usually prove to be impossible to print due to the fact that the models are usually made up of dozens, if not hundreds of non-manifold, open surfaces.
Not only is it a pain to make those models manifold without loosing a lot of detail, and putting hours of work in them, but making changes is nearly impossible unless I use the original program (3DS Max or whatever). Importing the meshes into Solidworks either gives me a distorted, useless solid, forces me to load the mesh as a non-editable object, or doesn't work at all.
So my point to the original thread was that due to the differences in the modeling structures, it's not always possible or practical to convert one file from a format to another and keep it editable.
I agree... but it is possible. I wrote the Modeling Basics sticky in the 3D Modeling subforum to help users understand why models may fail in polygonal modeling. It was never meant to be a How-To, just a "here's what you may need to know," but it serves its purpose if one reads is... maybe someday I'll get back to finish it (my family needs my time more and more, it seems). Still have a few more topics to address.
My CAD of choice is FreeCAD... not the best modeler out there, but it fits my budget (3 kids does that to ya)
Carrara is my polygonal of choice because I find it useful for more organic shapes and the workflow is pretty simplistic. Models from this software are not always scaled correctly, but for the more organic object I make, it's not an issue. I also use it for weapons design as I'm used to its modeling system. I just export the object and measure it in FreeCAD to get an approximate scaling to use in RH and I'm good to go.
As for importing someone else's error filled polygonal model, I don't use theirs, but rather build it from the ground up using their model as a guideline. I can usually eliminate the errors this way, but then again, I know how to model well for 3D printing in a polygonal modeler. All I need is scaling and I can almost always duplicate their model (sticking to the end user agreement set forth in Thingiverse). I usually post it as a re-work if I can so that others can benefit.
I've managed to import stl to Blender. Problem was that earlier i was importing binary files, but when i tried with ASCII it worked well and models are editable.
3d coat can import .stl's and has worked for me going from sketchup to 3d coat and back again. Beware opening up in sketchup after using voxel drawing, the triangles on the sketchup are formidable.
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