You could look at something like GiMP or Illustrator to convert a bitmap to
an SVG, and import that into OpenSCAD, but I'm pretty sure that process
will look a lot like the wiki-suggested route of using Inkscape.

In your thought above, you return back to ultimately working with a Bezier;
is that what you're looking for, or did you want to end up with a shape or
path to create a shape? Seems like if it's the former and you want a Bezier
curve, might just be worth it to bite down and trial-and-error till you're
comfy with them; and if it's the latter, then working from an SVG is what
you want?  Unless I'm misinterpreting what you're proposing above?

On Thu, Sep 19, 2024 at 5:29 PM Bob Carlson via Discuss <
discuss@lists.openscad.org> wrote:

--

• Jon Gilbert
  jong@jong.org / jgilbertsjc@gmail.com

It's not quite what you're looking for, but I wrote a graphical tool to
let me plot points and collect them into an OpenSCAD point list:

https://github.com/butcherg/wxpolygon

Doesn't do Beziers or anything like that, but it does let you define a
third number for a point, a radius, to be used by the Round-Anything
polyRound() module which will replace a point with a radius with a set
of points outlining the radius.

https://github.com/Irev-Dev/Round-Anything

I think BOSL2 may also have such a tool.

On 9/19/2024 6:29 PM, Bob Carlson via Discuss wrote:

Bezier curves have been implemented in various libraries, including BOSL2,
so if you can produce a bezier curve I'd say you've solved the problem.  I
don't think bezier curves are likely to ever appear in native OpenSCAD
because I got the impression that the developers see this as something
easily done in userspace.  I've started looking at a NURBS / B-spline
implementation, which I suspect will be easier to use for matching a
desired curve, but probably not ready for a while.

On Thu, Sep 19, 2024 at 9:32 PM William F. Adams via Discuss <
discuss@lists.openscad.org> wrote:

Can you quickly send a link to an (trivial example of how to create a
NURBS/B-Splint example using
BOSL2 ?
Would it be an option that users use the OpenSCAD customizer to rectify
the correct  curved face ?

On Fri, Sep 20, 2024 at 3:45 AM Adrian Mariano via Discuss <
discuss@lists.openscad.org> wrote:

While BOSL2 does have support for Bezier curves and surfaces, it does NOT have code to do B-Splines/NURBS.  About as close as it gets is the rather experimental code attached below.

• Revar



If you are trying to match an existing curve by taking points from the
existing curve then as per my understanding it is polynomial curve.

I don't think bezier can match than completely.
Maybe bspline if you have many points selected to match that curve.

To match a curve by picking few points especially where the curve is
changing direction, someone probably need to write polynomial curve.

It should be possible in openscad.

On Fri, 20 Sept, 2024, 5:59 am Bob Carlson via Discuss, <
discuss@lists.openscad.org> wrote:

On 9/19/2024 5:29 PM, Bob Carlson via Discuss wrote:

Funny you mention it now because I just spent many hours solving a
problem like that. All the while, I was wondering what kind of
functionality OpenSCAD might be able to integrate for this purpose.

I needed to replicate a bracket made out of thin acrylic.

I traced it on paper and annotated it with caliper measurements:

I opened Inkscape and decided it was too much to learn just then. I
remembered playing with SolveSpace before, the parametric solver, so I
opened that instead. It turned out to be easy to import an background
image and draw over it. Though it took me a while to figure out what to
do, but my final process was:

• Draw a closed curve comprising connected lines and arcs in the
  approximate shape (or just one half, because of symmetry).
• Apply constraints for tangency and parallelism. It actually gets
  pretty easy after playing around for a while. It's not necessary to
  fully constrain every single thing.
• Drag points around until it matches the picture.
• Extrude vertically and export as an STL mesh.

I wrote an OpenSCAD script to import the STL, scale it to actual size,
mirror the right half, punch holes, etc. Some of that was a bit tricky
because I had to create cutter cylinders and cubes and translate them to
the correct angles and positions by trial and error.

module bracket_half() {
     difference() {
         // The 0.973 makes the far side of the two pins 48.4 wide
         scale([63.2 / 2 / 8.196650 * 0.973, 97 / 23.864340, 4.5 /
8.972530])
             import("bracket.stl", convexity = 2);
         // Chop off some of the inside of the pins so the inside
distance is 19.6
         translate([-9.8, -44.4, -1])
             cube([9.8, 15.17, 5]);
         // Chop off wedges to make the pins trapezoidal
         translate([-7.47, -44.25, -5])
             rotate([0, -25, 0])
                 cube([15, 15, 15]);
         translate([-26.54, -44.25, -5])
             rotate([0, -65, 0])
                 cube([15, 15, 15]);
     }
}

module bracket()
     difference() {
         union() {
             bracket_half();
             mirror([1, 0, 0])
                 bracket_half();
         }
         // Bottom hole
         translate([0, 30.5, -1])
            cylinder(d = 8, h = 10, $fn = 60);
         // Top hole
         translate([0, 45.1, -1])
            cylinder(d = 8, h = 10, $fn = 60);
         // Round off the top divot
         translate([0, 57.31, -1])
             scale([9.5, 1, 1])
                 cylinder(d = 1, h = 7, $fn = 60);
         // Take 2mm off the pins
         translate([0, -48, -5])
             cube([100, 20, 20], center = true);
     }

//bracket_half();
bracket();

I was then able to print two in Overture Transparent PETG. I followed
some "printing glass" instructions from the Web, but this'll have to do.
It was done for a friend, mostly for fun, and the amount of time
required (at my pre-retirement pay grade) would have cost something
upwards of $1000 (kind of ridiculous :).

Besides drawing 2D curves, SolveSpace does complicated 3D objects.
Wouldn't it be nice if you could write parametric statements in OpenSCAD
like "make a sphere tangent to this face of this cube and passing
through this point on this other cube"? Referencing previously defined
objects might be a lot easier in Python SCAD.

Regards,
Curt