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

Jordan Brown openscad at jordan.maileater.net
Tue Nov 12 13:31:47 EST 2019


On 11/11/2019 11:19 PM, nop head wrote:
> Since all real objects are 2-manifold I don't see why OpenSCAD needs
> to be able to handle non-manifold designs. What advantage is it?

Not having to take care to never allow two objects to touch?  Not having
to explain to people what "manifold" means?

(This isn't contrived; I've had real modeling cases where two objects
happened to touch at a single point.  I had to figure out what was
happening and then artificially tweak them apart.)

> If you want to print two cubes next to each then leave a small gap.

Why?  Why should I have to do this, when the intent is obvious?

> They will then get two separate perimeters. If you want to print two
> cubes that are joined overlap them by your printers minimum wall
> width. Your model then represents what  you want your printer to
> print. If you export two cubes sharing an edge who knows what the
> printer will do? It is much better to give an error as soon as
> possible to avoid creating a model that can't be printed. Yes the
> printer may print something but it won't match the physically
> impossible model.

My point is that *it doesn't matter* what the printer does.

Why is there any practical difference between two cubes that share an
edge, two cubes that are separated by a micrometer, and two cubes that
overlap by a micrometer?  The printer's resolution isn't anywhere near
that small. It can't match *any* of the three, yet the software treats
them all as fundamentally different, and considers two "possible" and
the third "impossible".

When you say "can't be printed", do you mean "that the software can't
handle", or do you mean "where what is printed does not perfectly match
the mathematical model"?  If the software can't handle it, that's
exactly the problem I'd like to see solved.  If the printed object does
not perfectly match the mathematical model... *nothing* printed ever
perfectly matches the mathematical model.  cube(100) is supposed to
generate a cube 100 units on a side.  What gets printed is the result of
mushing together a bunch of cylinders of plastic - the sides aren't
flat, the edges are round instead of right angles, and it's measurably
off 100 units.  Printing is *always* an approximation of the
mathematical model.

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