[OpenSCAD] User Poll: What do you want to see from OpenSCAD development?

Doug Moen doug at moens.org
Mon Nov 11 08:51:16 EST 2019


On Mon, Nov 11, 2019, at 7:33 AM, nop head wrote:
> Regardless of file format limitations, non manifold objects cannot exist in reality, so I think it should be an error to make one and users should be educated.
> 
> Two cubes cannot share a zero width edge. They either overlap by at least one atom or are separate. It is no coincidence that STL can represents all physically realisable objects.

I disagree! 3MF is a file format for 3D printing. It was designed by a group of technical experts from 3D printer companies (like 3D systems) and 3D service providers (like Shapeways). The 3MF standard goes into great detail explaining what is and is not a valid mesh, and it provides instructions on how slicers should interpret valid 3MF meshes. It is an impressive document, obviously written by people who understand 3D printing.

So it's hard to understand your belief that valid 3MF meshes are not "physically realizable". 3MF meshes are 3D printable, so how can it simultaneously be true that they aren't "physically realizable"?

OpenSCAD should be able to import, process and export any valid 3MF mesh, including meshes that would not be valid if converted to STL format. We can't do that today, but it is a useful goal to have for the future.

I have a Prusa i3 at home, and I was inspired to start this conversation after reading that 3MF is now the preferred file format at Prusa. This is because:
 * 3MF is an open standard (Unlike AMF. You have to pay money to read the AMF standard.)
 * 3MF is unambiguous. There are rules that determine what is a valid mesh. Given a valid mesh, there are rules on how to interpret it for slicing. AMF (says Prusa) is ambiguous.
 * 3MF files are significantly more compact than STL files.
 * They can represent multi-colour and multi-material models (important if you have the Prusa multi-material unit). Unlike STL.
 * They can store slicer configuration which describes how to slce this particular model. Unlike STL.
 PrusaSlicer can save config changes back to the original 3MF file.

So I'd like to see better 3MF support in the future.
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