Tool idea for matching complex curves
I have a rounded_polygon module to make shapes that are arcs joined by
tangents.
https://github.com/nophead/NopSCADlib?tab=readme-ov-file#rounded_polygon
Polynomial curves through large numbers of points tend to go wild. I have
cubic splines and catmull-rom splines that are better behaved between the
points. https://github.com/nophead/NopSCADlib?tab=readme-ov-file#splines
I modelled this toilet seat bumper using Bezier splines. I guessed the
inner two control points and it seemed spot-on at first guess.
[image: IMG_20231218_202013684.jpg]
[image: IMG_20231218_200902247.jpg]
module curve(end)
translate([end * (length - width) / 2, 0])
rotate_extrude($fa = 1)
polygon([
[0, 0],
[0, height],
each bezier_path([
[width / 2, height],
[width / 2, height - 2],
[width / 2, 0],
[flat_width / 2, 0],
]),
]);
On Fri, 20 Sept 2024 at 08:46, Curt McDowell via Discuss <
discuss@lists.openscad.org> wrote:
On 9/19/2024 5:29 PM, Bob Carlson via Discuss wrote:
Is there a tool like this already out there? I played around a little with InkScape, but didn’t see an easy way to use it.
I keep facing the problem of creating a curve in OpenSCAD that matches the one on a physical item. Bézier curves seems like a likely way to represent the curve but I have never used them because it just seemed like a LOT of trial and error was the only way. I have thought about what a tool would look like and here is the outline of it.
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
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On 20.09.2024 08:55, Guenther Sohler via Discuss 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 ?
This may not be exactly what you are looking for, but in AngelCAD you
can define 2d or 3d splines (spline2d & spline3d) from arrays of
measured positions on your curve. Once you have a spline, you can
extract positions (and derivatives) from it using normalized parameter t
in range (0,1). Such positions can be used to construct e.g. a polygon
which you can export to OpenSCAD .csg format. You can copy such a
polygon into your scad script.
Maybe you could implement something similar directly in OpenSCAD, but
the language makes it kind of difficult.
Carsten Arnholm
On Fri, Sep 20, 2024 at 5:06 AM Jordan Brown via Discuss <
discuss@lists.openscad.org> wrote:
What you describe is pretty much what I've done. I bring the JPEG into a
tool like InkScape or CorelDraw, match the shapes with Bézier curves, and
then read out the control point coordinates and transcribe them into my
OpenSCAD program's calls to Bézier-generating functions.
The manual transcription is a bit of a pain, but not awful for modestly
complex shapes
I had a similar problem, except I needed to export the Bezier code to the
Javascript API used for FreeSewing.org sewing patterns. I wrote an Inkscape
plugin that takes Bezier curves in Inkscape and outputs code for it. It
would be quite easy to adapt this plugin to create any other type of
Bezier-in-code-specification. My Inkscape plugin is on
https://github.com/roel-v/inkscape_to_fs_js .
Regarding the OP's remark that it's not so easy to make Beziers match
curves on an imported bitmap, there is indeed some initial learning to be
done, but have gotten quite adept at estimating where I need to put control
points to approximate any curve to an appropriate amount of detail, as well
as gotten acquainted with the Inkscape Bezier tools, which help a lot in
creating smooth, good looking and well fitting curves; I takes in the order
of magnitude of hours to learn these skills. So yes it takes some learning
but it's going to be a much better experience learning a mature existing
tool than dreaming up, and implementing, another tool that will invariably
take years and hundreds of man hours to grow into a fully fledged solution
like the one Inkscape is today.
cheers
As I stated, I am working on NURBS for BOSL2. I didn't not say it's
ready for use yet. The code I have is better than what Revar posted, but
it has bugs with repeated knots and bugs with closed curves (that don't
close exactly) so it's not ready to show to people. It needs to be
possible to sample the curve in a way that guarantees you hit each knot
location (because there might be corners there). It also only supports
uniform knots at the moment. It's unclear if this is really a major
limitation or not.
Regarding the problem in this thread, there is a simple way to use BOSL2 to
trace a desired curve with beziers, which is to use smooth_path(). It
constructs a cubic bezier path that goes through a list of points and
connects them with curved segments that join smoothly at the points.
https://github.com/BelfrySCAD/BOSL2/wiki/rounding.scad#function-smooth_path
On Fri, Sep 20, 2024 at 3:14 AM Revar Desmera 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
On Sep 19, 2024, at 11:55 PM, Guenther Sohler 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:
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:
Usually if they wish to work with something interactively folks just
import the pixel image into a tool such as Inkscape, re-draw it, then make
use of the SVG.
https://community.carbide3d.com/t/making-a-guitar-bridge-for-carbide-create-pro/70058
I'd love to see a simple OpenSCAD option, but solutions in this space
always tend to multiply numbers and have quite complex interfaces, and the
implementation goes even further down this road since one has to solve for
the Bézier curve as a series of straight-line moves.
Some sort of native Bézier curve support would be ideal, and has been
asked after/discussed here in the past, but doesn't seem to be on anyone's
radar or compatible with the roadmap of the project as a whole (I'd love to
be wrong).
William
--
Sphinx of black quartz, judge my vow.
https://designinto3d.com/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
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Thank you for all the impressions.
The Rounded Path is definitely a really nice thing!
But did we change topic ?
We were once talking about surfaces and I am still looking for
ideas/implementations on how to create surfaces with splines/nurbs with 3d
points on a surface given as control points.
On Fri, Sep 20, 2024 at 12:44 PM Adrian Mariano via Discuss <
discuss@lists.openscad.org> wrote:
As I stated, I am working on NURBS for BOSL2. I didn't not say it's
ready for use yet. The code I have is better than what Revar posted, but
it has bugs with repeated knots and bugs with closed curves (that don't
close exactly) so it's not ready to show to people. It needs to be
possible to sample the curve in a way that guarantees you hit each knot
location (because there might be corners there). It also only supports
uniform knots at the moment. It's unclear if this is really a major
limitation or not.
Regarding the problem in this thread, there is a simple way to use BOSL2
to trace a desired curve with beziers, which is to use smooth_path(). It
constructs a cubic bezier path that goes through a list of points and
connects them with curved segments that join smoothly at the points.
https://github.com/BelfrySCAD/BOSL2/wiki/rounding.scad#function-smooth_path
On Fri, Sep 20, 2024 at 3:14 AM Revar Desmera 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
On Sep 19, 2024, at 11:55 PM, Guenther Sohler 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:
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:
Usually if they wish to work with something interactively folks just
import the pixel image into a tool such as Inkscape, re-draw it, then make
use of the SVG.
https://community.carbide3d.com/t/making-a-guitar-bridge-for-carbide-create-pro/70058
I'd love to see a simple OpenSCAD option, but solutions in this space
always tend to multiply numbers and have quite complex interfaces, and the
implementation goes even further down this road since one has to solve for
the Bézier curve as a series of straight-line moves.
Some sort of native Bézier curve support would be ideal, and has been
asked after/discussed here in the past, but doesn't seem to be on anyone's
radar or compatible with the roadmap of the project as a whole (I'd love to
be wrong).
William
--
Sphinx of black quartz, judge my vow.
https://designinto3d.com/
OpenSCAD mailing list
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This particular topic was about paths, not surfaces. Creating surfaces
seems a much more difficult task, assuming the surface isn't trivially
related to a curve. I've only been able to do this myself with very
constrained situations such as rounded_prism() and join_prism() where the
surface to be constructed is constrained by other shapes in a simple way.
This doesn't lead to an elephant or a tea pot.
On Fri, Sep 20, 2024 at 7:03 AM Guenther Sohler via Discuss <
discuss@lists.openscad.org> wrote:
Thank you for all the impressions.
The Rounded Path is definitely a really nice thing!
But did we change topic ?
We were once talking about surfaces and I am still looking for
ideas/implementations on how to create surfaces with splines/nurbs with 3d
points on a surface given as control points.
On Fri, Sep 20, 2024 at 12:44 PM Adrian Mariano via Discuss <
discuss@lists.openscad.org> wrote:
As I stated, I am working on NURBS for BOSL2. I didn't not say it's
ready for use yet. The code I have is better than what Revar posted, but
it has bugs with repeated knots and bugs with closed curves (that don't
close exactly) so it's not ready to show to people. It needs to be
possible to sample the curve in a way that guarantees you hit each knot
location (because there might be corners there). It also only supports
uniform knots at the moment. It's unclear if this is really a major
limitation or not.
Regarding the problem in this thread, there is a simple way to use BOSL2
to trace a desired curve with beziers, which is to use smooth_path(). It
constructs a cubic bezier path that goes through a list of points and
connects them with curved segments that join smoothly at the points.
https://github.com/BelfrySCAD/BOSL2/wiki/rounding.scad#function-smooth_path
On Fri, Sep 20, 2024 at 3:14 AM Revar Desmera 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
On Sep 19, 2024, at 11:55 PM, Guenther Sohler 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:
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:
Usually if they wish to work with something interactively folks just
import the pixel image into a tool such as Inkscape, re-draw it, then make
use of the SVG.
https://community.carbide3d.com/t/making-a-guitar-bridge-for-carbide-create-pro/70058
I'd love to see a simple OpenSCAD option, but solutions in this space
always tend to multiply numbers and have quite complex interfaces, and the
implementation goes even further down this road since one has to solve for
the Bézier curve as a series of straight-line moves.
Some sort of native Bézier curve support would be ideal, and has been
asked after/discussed here in the past, but doesn't seem to be on anyone's
radar or compatible with the roadmap of the project as a whole (I'd love to
be wrong).
William
--
Sphinx of black quartz, judge my vow.
https://designinto3d.com/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
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I do something similar to William. I pull the image into an image
viewer that I wrote, which has a feature where you can click along a
curve and a text file is generated with the X/Y coordinates that you
clicked. I then modify it into a point list that can be used by
OpenSCAD and use rounding (BOSL2) to get the shape that I want. I'm
sure that this can be done in Inkscape and GIMP using layers.
On 9/19/2024 9:31 PM, William F. Adams via Discuss wrote:
Usually if they wish to work with something interactively folks just import the pixel image into a tool such as Inkscape, re-draw it, then make use of the SVG.
https://community.carbide3d.com/t/making-a-guitar-bridge-for-carbide-create-pro/70058
I'd love to see a simple OpenSCAD option, but solutions in this space always tend to multiply numbers and have quite complex interfaces, and the implementation goes even further down this road since one has to solve for the Bézier curve as a series of straight-line moves.
Some sort of native Bézier curve support would be ideal, and has been asked after/discussed here in the past, but doesn't seem to be on anyone's radar or compatible with the roadmap of the project as a whole (I'd love to be wrong).
William
--
This email has been checked for viruses by AVG antivirus software.
www.avg.com
I admire the effort put into BOSL2, but I wonder why would you write
NURBS in openscad instead of trying to push it into openscad itself?
From my experience the interpreter of openscad is quite slow, and data
structure is quite limited, which makes the hard task of writing a NURBS
engine even harder and slower. Also, as openscad doesn't have the
ability to inspect mesh results (at least for now), this makes the
workflow of using these features very different from the typical usage
of openscad.
On 20/9/2024 18:43, Adrian Mariano via Discuss wrote:
As I stated, I am working on NURBS for BOSL2. I didn't not say it's
ready for use yet. The code I have is better than what Revar posted,
but it has bugs with repeated knots and bugs with closed curves (that
don't close exactly) so it's not ready to show to people. It needs to
be possible to sample the curve in a way that guarantees you hit each
knot location (because there might be corners there). It also only
supports uniform knots at the moment. It's unclear if this is really
a major limitation or not.
Regarding the problem in this thread, there is a simple way to use
BOSL2 to trace a desired curve with beziers, which is to use
smooth_path(). It constructs a cubic bezier path that goes through a
list of points and connects them with curved segments that join
smoothly at the points.
https://github.com/BelfrySCAD/BOSL2/wiki/rounding.scad#function-smooth_path
On Fri, Sep 20, 2024 at 3:14 AM Revar Desmera 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
On Sep 19, 2024, at 11:55 PM, Guenther Sohler 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:
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:
Usually if they wish to work with something interactively
folks just import the pixel image into a tool such as
Inkscape, re-draw it, then make use of the SVG.
https://community.carbide3d.com/t/making-a-guitar-bridge-for-carbide-create-pro/70058
I'd love to see a simple OpenSCAD option, but solutions
in this space always tend to multiply numbers and have
quite complex interfaces, and the implementation goes
even further down this road since one has to solve for
the Bézier curve as a series of straight-line moves.
Some sort of native Bézier curve support would be ideal,
and has been asked after/discussed here in the past, but
doesn't seem to be on anyone's radar or compatible with
the roadmap of the project as a whole (I'd love to be wrong).
William
--
Sphinx of black quartz, judge my vow.
https://designinto3d.com/
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On Sep 20, 2024, at 5:39 AM, Chun Kit LAM via Discuss discuss@lists.openscad.org wrote:
I admire the effort put into BOSL2, but I wonder why would you write NURBS in openscad instead of trying to push it into openscad itself? From my experience the interpreter of openscad is quite slow, and data structure is quite limited, which makes the hard task of writing a NURBS engine even harder and slower. Also, as openscad doesn't have the ability to inspect mesh results (at least for now), this makes the workflow of using these features very different from the typical usage of openscad.
To be delicate about the issue, without trying to instigate a flame war, the fact that they CAN be done by a library is take as evidence that they SHOULD be, by the current powers that be.
-Revar
To be delicate about the issue, without trying to instigate a flame war,
the fact that they CAN be done by a library is take as evidence that they
SHOULD be, by the current powers that be.
One point in favor of doing it in a library is the implementation is
accessible to all users while anything built into OpenSCAD is only fully
accessible to those willing and able to set up an OpenSCAD development
environment. I'm very thankful for the libraries which aren't just merely
useful but are teaching me what is possible as a user of OpenSCAD and
provide many examples of how I can do things better than I have or likely
ever would have figured out on my own from the OpenSCAD documentation.
On Fri, Sep 20, 2024 at 11:17 AM Revar Desmera via Discuss <
discuss@lists.openscad.org> wrote:
On Sep 20, 2024, at 5:39 AM, Chun Kit LAM via Discuss <
discuss@lists.openscad.org> wrote:
I admire the effort put into BOSL2, but I wonder why would you write NURBS
in openscad instead of trying to push it into openscad itself? From my
experience the interpreter of openscad is quite slow, and data structure is
quite limited, which makes the hard task of writing a NURBS engine even
harder and slower. Also, as openscad doesn't have the ability to inspect
mesh results (at least for now), this makes the workflow of using these
features very different from the typical usage of openscad.
To be delicate about the issue, without trying to instigate a flame war,
the fact that they CAN be done by a library is take as evidence that they
SHOULD be, by the current powers that be.
-Revar
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