@theoutside Almost everyone sends triangulated STL files to 3D printers. I don’t. I send quadrangulated OBJ files to the printers. The STL files have two big flaws: they cannot use quad-shaped mesh faces and they have no vertex normals (only face normals). Their only advantage is binary format. OBJ files do not have these flaws. Their only flaw is that they are not binary. This is minor flaw because they can be compressed. RAR format reduces their size 4 times. ZIP format reduces their size 3 times. When I finish NURBS modelling, I make pretty quad meshes with Rhino WIP QuadRemesh command and I export them to the OBJ file format. (Rhino 6 can also make quad meshes with the help of a plugin called CreateQuadMesh, but this plugin is inferior to the QuadRemesh command in many ways.)
hi Andrew 3 questions:
why do you prefer quad meshes for 3d printing?
whats the advantage of having vertex normals? (i guess this is not aimed at 3d printing)
why do you think binary is better?
QuadRemesh command makes perfect, beautiful meshes.
They help define the surface well. (I do not know how many 3D printers use this data, but they should use it when it is available.)
Binary files are several times smaller than text files.
- Quads are just under-defined triangles.
All Quads that are not coplanar are basically incomplete triangles. If you do this the slicing software will decide for you where to place a triangle, and you have no control over it:
- Don’t trust or try to use vertex normals.
Vertex normals are not true geometric information, they are not defining topology in any way, but rather point information that only affects lighting and reflection:
…in fact when evaluating a meshes part before exporting to .STL you should always look at it in flat shade mode (a toggle in the display tab). So you can see what you are truly sending to the 3D printer.
In summary: don’t work with quad or with vertex normals for 3D printing if what you see on your screen is what you expect to see printed.
In contrast to the statement in your thread title using quad meshes has no advantage whatsoever in 3D printing. It’s therefore silly to spend time turning existing meshes to quads, before sending them to the printer. You got the same answer in previous threads already.
that is what i thought, but if you keep objects unaltered out of the printer, the retopologized quad mesh can be a pretty amendment. that is probably the sole advantage.
What does that mean?
What’s the advantage again? I’m confused. Is it that the quads looks pretty?
some sand it, use acetone or other technics to smoothen down the surface
yup
Making quad meshes has nothing to do with 3D printing as has been said, and are we talking about making files to send to a service bureau or to your own printer? Any good service bureau will take NURBS files and deal with those stupid nasty meshes themselves. For your own printer…well STL stinks but I don’t see how one format for a dumb list of points is better than another.
nobody claimed it has, besides the optical effect but i guess the confusion is just getting bigger.
Hmm, that’s the whole premise of this post, that somehow a “nicer-looking” (if on-screen only) mesh file is somehow better for printing. That makes no sense but that’s exactly what’s being claimed.
Oooh, do you are saying making the quad flow/structure as a texturing/tessellation visible on the part. Yeah that does make sense now. Thx
yup, that was the idea i believe, before we ponder even deeper into this mysterious topic 
If you want to minimize file size of a mesh which has high Gaussian curvature, all its faces should approximate circles. The best examples of this rule are geodesic grids - the most efficient grids are made of hexagons and pentagons. Quad meshes are useful because square is better approximation of the circle than equilateral triangle. Elongated rectangles are better suited for approximating cylinders than triangles. Triangles are better than rectangles for approximating cones.
We really need new file format optimized for 3D printing. For the sake of simplicity, it should be restricted to triangular and quadrangular meshes. It would be good idea to include information where supports may be added.
People have tried… there are a number of initiatives out there, but .stl just keeps on keepin’ on despite the better alternatives.
Yeah, presumably because no one is going to spend $$$ on developing a public format.
AMF with “curved” triangles, neat idea for allowing improved geometry. Any support for exporting/importing AMF I have seen in a commercial product did not support the new geometry.
To be fair, I have not looked at this in many years since I figured it it wasn’t completely supported, what was the point in using it.
If I’m wrong, someone please correct me.
“STL is not tailored for additive manufacturing because it generates large file sizes of topology optimized parts and lattice structures due to the large number of surfaces involved.” source: https://en.wikipedia.org/wiki/3D_printing
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“Additive manufacturing file format (AMF) is an open standard for describing objects for additive manufacturing processes such as 3D printing. The official ISO/ASTM 52915:2016 standard is an XML-based format designed to allow any computer-aided design software to describe the shape and composition of any 3D object to be fabricated on any 3D printer. Unlike its predecessor STL format, AMF has native support for color, materials, lattices, and constellations… In order to improve geometric fidelity, the format allows curving the triangle patches. By default, all triangles are assumed to be flat and all triangle edges are assumed to be straight lines connecting their two vertices. However, curved triangles and curved edges can optionally be specified in order to reduce the number of mesh elements required to describe a curved surface. The curvature information has been shown to reduce the error of a spherical surface by a factor of 1000 as compared to a surface described by the same number of planar triangles.” source: https://en.wikipedia.org/wiki/Additive_manufacturing_file_format
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“3D Manufacturing Format or 3MF is an open source file format standard developed and published by the 3MF Consortium. 3MF is an XML-based data format designed for using additive manufacturing, including information about materials, colors, and other information that cannot be represented in the STL format. As of today, CAD software related companies such as Autodesk, Dassault Systemes and Netfabb are part of the 3MF Consortium. Other firms in the 3MF Consortium are Microsoft (for operating system and 3D modeling support), SLM and HP, whilst Shapeways are also included to give insight from a 3D Printing background. Other key players in the 3D printing and additive manufacturing business, such as Materialise, 3D Systems, Siemens PLM Software and Stratasys have recently joined the consortium.” source: https://en.wikipedia.org/wiki/3D_Manufacturing_Format
Yeah, I’ve read the Wiki and I suspect reality differs a bit from what that says.
Although the format spec may be public, what company will spend (or has spent?) to develop the code to write the new geometry from their system?
The “curved” triangle geometry is indicated as an “optional” part of the spec according to the Wiki.