discuss@lists.openscad.org

OpenSCAD general discussion Mailing-list

View all threads

Minkowski error on object scaled with negative value

SL
Steve Lelievre
Mon, Dec 23, 2024 12:10 AM

Nightly 2024.12.21 on Windows 10 gives me an error message when
rendering the following code

x = -15;
$fn = 60;
minkowski() {
  scale([1, 1, x]) roof() hull() {
    circle(d = 15);
    translate([0, 6]) circle(d = 6);
  }
  sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to Nef
operation: CGAL ERROR: assertion violation!
Expr: e->incident_sface() != SFace_const_handle()
File:
/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 329
ERROR: The given mesh is not closed! Unable to convert to
CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the
resulting shape by adding "scale([1,1,-1])" just  before the minkowski.
The issue can also be removed by reducing the value of $fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an explanation
of the cause - in particular why it works okay for x = +15 but not x =
-15 (to me, it's just symmetry so sign inversion should not make a
difference.)

Cheers,

Steve

Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code x = -15; $fn = 60; minkowski() {   scale([1, 1, x]) roof() hull() {     circle(d = 15);     translate([0, 6]) circle(d = 6);   }   sphere(d = 0.06); } The message produced is WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation! Expr: e->incident_sface() != SFace_const_handle() File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h Line: 329 ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron. I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just  before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less. Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.) Cheers, Steve
MK
Marius Kintel
Mon, Dec 23, 2024 4:44 PM

Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()?

-Markus

On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss discuss@lists.openscad.org wrote:

Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code

x = -15;
$fn = 60;
minkowski() {
scale([1, 1, x]) roof() hull() {
circle(d = 15);
translate([0, 6]) circle(d = 6);
}
sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation!
Expr: e->incident_sface() != SFace_const_handle()
File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 329
ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just  before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.)

Cheers,

Steve


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()? -Markus > On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss <discuss@lists.openscad.org> wrote: > > Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code > > x = -15; > $fn = 60; > minkowski() { > scale([1, 1, x]) roof() hull() { > circle(d = 15); > translate([0, 6]) circle(d = 6); > } > sphere(d = 0.06); > } > > > The message produced is > > WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation! > Expr: e->incident_sface() != SFace_const_handle() > File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h > Line: 329 > ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron. > > I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less. > > Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.) > > > Cheers, > > Steve > > > > > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org
SL
Steve Lelievre
Mon, Dec 23, 2024 8:45 PM

Hi,

Further testing shows that my problem happens only when I use roof to
define the initial 3D shape, and that it works just fine with roof
method 'straight'. As well, I found a simpler failing case (no hull):

minkowski() {
  scale([1, 1, -15]) roof() circle(d = 15, $fn = 60);
  sphere(d  = 1);
}

The problem can be made to go away by choosing other values for the z
scaling, the circle diameter, or the circle facet number.

Steve

On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote:

Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()?

-Markus

On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss discuss@lists.openscad.org wrote:

Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code

x = -15;
$fn = 60;
minkowski() {
scale([1, 1, x]) roof() hull() {
circle(d = 15);
translate([0, 6]) circle(d = 6);
}
sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation!
Expr: e->incident_sface() != SFace_const_handle()
File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 329
ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just  before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.)

Cheers,

Steve


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

Hi, Further testing shows that my problem happens only when I use roof to define the initial 3D shape, and that it works just fine with roof method 'straight'. As well, I found a simpler failing case (no hull): minkowski() {   scale([1, 1, -15]) roof() circle(d = 15, $fn = 60);   sphere(d  = 1); } The problem can be made to go away by choosing other values for the z scaling, the circle diameter, or the circle facet number. Steve On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote: > Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()? > > -Markus > >> On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss <discuss@lists.openscad.org> wrote: >> >> Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code >> >> x = -15; >> $fn = 60; >> minkowski() { >> scale([1, 1, x]) roof() hull() { >> circle(d = 15); >> translate([0, 6]) circle(d = 6); >> } >> sphere(d = 0.06); >> } >> >> >> The message produced is >> >> WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation! >> Expr: e->incident_sface() != SFace_const_handle() >> File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h >> Line: 329 >> ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron. >> >> I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less. >> >> Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.) >> >> >> Cheers, >> >> Steve >> >> >> >> >> >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org -- https://www.gnomoni.ca https://www.youtube.com/@gnomonica
MK
Marius Kintel
Mon, Dec 23, 2024 9:09 PM

Thanks for confirming. This could be a bug in roof(); roof is still very experimental and have some rough corners.
Could you open an issue on https://github.com/openscad/openscad/issues and include your minimal example?

-Marius

On Dec 23, 2024, at 15:45, Steve Lelievre via Discuss discuss@lists.openscad.org wrote:

Hi,

Further testing shows that my problem happens only when I use roof to define the initial 3D shape, and that it works just fine with roof method 'straight'. As well, I found a simpler failing case (no hull):

minkowski() {
scale([1, 1, -15]) roof() circle(d = 15, $fn = 60);
sphere(d  = 1);
}

The problem can be made to go away by choosing other values for the z scaling, the circle diameter, or the circle facet number.

Steve

On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote:

Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()?

-Markus

On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss discuss@lists.openscad.org wrote:

Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code

x = -15;
$fn = 60;
minkowski() {
scale([1, 1, x]) roof() hull() {
circle(d = 15);
translate([0, 6]) circle(d = 6);
}
sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation!
Expr: e->incident_sface() != SFace_const_handle()
File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 329
ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just  before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.)

Cheers,

Steve


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

--
https://www.gnomoni.ca
https://www.youtube.com/@gnomonica


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

Thanks for confirming. This could be a bug in roof(); roof is still very experimental and have some rough corners. Could you open an issue on https://github.com/openscad/openscad/issues and include your minimal example? -Marius > On Dec 23, 2024, at 15:45, Steve Lelievre via Discuss <discuss@lists.openscad.org> wrote: > > Hi, > > Further testing shows that my problem happens only when I use roof to define the initial 3D shape, and that it works just fine with roof method 'straight'. As well, I found a simpler failing case (no hull): > > minkowski() { > scale([1, 1, -15]) roof() circle(d = 15, $fn = 60); > sphere(d = 1); > } > > The problem can be made to go away by choosing other values for the z scaling, the circle diameter, or the circle facet number. > > Steve > > > > > On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote: >> Does this only fail when using roof(), or are you able to reproduce similar behavior also without roof()? >> >> -Markus >> >>> On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss <discuss@lists.openscad.org> wrote: >>> >>> Nightly 2024.12.21 on Windows 10 gives me an error message when rendering the following code >>> >>> x = -15; >>> $fn = 60; >>> minkowski() { >>> scale([1, 1, x]) roof() hull() { >>> circle(d = 15); >>> translate([0, 6]) circle(d = 6); >>> } >>> sphere(d = 0.06); >>> } >>> >>> >>> The message produced is >>> >>> WARNING: [manifold] Minkowski failed with error, falling back to Nef operation: CGAL ERROR: assertion violation! >>> Expr: e->incident_sface() != SFace_const_handle() >>> File: /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h >>> Line: 329 >>> ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron. >>> >>> I can circumvent the problem by using x = +15 and inverting the resulting shape by adding "scale([1,1,-1])" just before the minkowski. The issue can also be removed by reducing the value of $fn to 28 or less. >>> >>> Although I can avoid the issue, I'd be interested to hear an explanation of the cause - in particular why it works okay for x = +15 but not x = -15 (to me, it's just symmetry so sign inversion should not make a difference.) >>> >>> >>> Cheers, >>> >>> Steve >>> >>> >>> >>> >>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> To unsubscribe send an email to discuss-leave@lists.openscad.org >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > -- > https://www.gnomoni.ca > https://www.youtube.com/@gnomonica > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org
SL
Steve Lelievre
Mon, Dec 23, 2024 9:12 PM

Will do.

Thanks for your hard work.

Steve

On 2024-12-23 1:09 p.m., Marius Kintel via Discuss wrote:

Thanks for confirming. This could be a bug in roof(); roof is still
very experimental and have some rough corners.
Could you open an issue on
https://github.com/openscad/openscad/issues and include your minimal
example?

 -Marius

Will do. Thanks for your hard work. Steve On 2024-12-23 1:09 p.m., Marius Kintel via Discuss wrote: > Thanks for confirming. This could be a bug in roof(); roof is still > very experimental and have some rough corners. > Could you open an issue on > https://github.com/openscad/openscad/issues and include your minimal > example? > >  -Marius
GS
Guenther Sohler
Mon, Dec 23, 2024 11:12 PM

This smells like roof is creating wrong oriented faces ...

On Mon, Dec 23, 2024 at 9:46 PM Steve Lelievre via Discuss <
discuss@lists.openscad.org> wrote:

Hi,

Further testing shows that my problem happens only when I use roof to
define the initial 3D shape, and that it works just fine with roof
method 'straight'. As well, I found a simpler failing case (no hull):

minkowski() {
scale([1, 1, -15]) roof() circle(d = 15, $fn = 60);
sphere(d  = 1);
}

The problem can be made to go away by choosing other values for the z
scaling, the circle diameter, or the circle facet number.

Steve

On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote:

Does this only fail when using roof(), or are you able to reproduce

similar behavior also without roof()?

-Markus

On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss <

Nightly 2024.12.21 on Windows 10 gives me an error message when

rendering the following code

x = -15;
$fn = 60;
minkowski() {
scale([1, 1, x]) roof() hull() {
circle(d = 15);
translate([0, 6]) circle(d = 6);
}
sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to Nef

operation: CGAL ERROR: assertion violation!

Expr: e->incident_sface() != SFace_const_handle()
File:

/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h

Line: 329
ERROR: The given mesh is not closed! Unable to convert to

CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the

resulting shape by adding "scale([1,1,-1])" just  before the minkowski. The
issue can also be removed by reducing the value of $fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an

explanation of the cause - in particular why it works okay for x = +15 but
not x = -15 (to me, it's just symmetry so sign inversion should not make a
difference.)

Cheers,

Steve


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

--
https://www.gnomoni.ca
https://www.youtube.com/@gnomonica


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

This smells like roof is creating wrong oriented faces ... On Mon, Dec 23, 2024 at 9:46 PM Steve Lelievre via Discuss < discuss@lists.openscad.org> wrote: > Hi, > > Further testing shows that my problem happens only when I use roof to > define the initial 3D shape, and that it works just fine with roof > method 'straight'. As well, I found a simpler failing case (no hull): > > minkowski() { > scale([1, 1, -15]) roof() circle(d = 15, $fn = 60); > sphere(d = 1); > } > > The problem can be made to go away by choosing other values for the z > scaling, the circle diameter, or the circle facet number. > > Steve > > > > > On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote: > > Does this only fail when using roof(), or are you able to reproduce > similar behavior also without roof()? > > > > -Markus > > > >> On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss < > discuss@lists.openscad.org> wrote: > >> > >> Nightly 2024.12.21 on Windows 10 gives me an error message when > rendering the following code > >> > >> x = -15; > >> $fn = 60; > >> minkowski() { > >> scale([1, 1, x]) roof() hull() { > >> circle(d = 15); > >> translate([0, 6]) circle(d = 6); > >> } > >> sphere(d = 0.06); > >> } > >> > >> > >> The message produced is > >> > >> WARNING: [manifold] Minkowski failed with error, falling back to Nef > operation: CGAL ERROR: assertion violation! > >> Expr: e->incident_sface() != SFace_const_handle() > >> File: > /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h > >> Line: 329 > >> ERROR: The given mesh is not closed! Unable to convert to > CGAL_Nef_Polyhedron. > >> > >> I can circumvent the problem by using x = +15 and inverting the > resulting shape by adding "scale([1,1,-1])" just before the minkowski. The > issue can also be removed by reducing the value of $fn to 28 or less. > >> > >> Although I can avoid the issue, I'd be interested to hear an > explanation of the cause - in particular why it works okay for x = +15 but > not x = -15 (to me, it's just symmetry so sign inversion should not make a > difference.) > >> > >> > >> Cheers, > >> > >> Steve > >> > >> > >> > >> > >> > >> _______________________________________________ > >> OpenSCAD mailing list > >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > _______________________________________________ > > OpenSCAD mailing list > > To unsubscribe send an email to discuss-leave@lists.openscad.org > > -- > https://www.gnomoni.ca > https://www.youtube.com/@gnomonica > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
SL
Steve Lelievre
Tue, Dec 24, 2024 2:07 AM

Issue #5528

On 2024-12-23 1:09 p.m., Marius Kintel via Discuss wrote:

Thanks for confirming. This could be a bug in roof(); roof is still
very experimental and have some rough corners.
Could you open an issue on
https://github.com/openscad/openscad/issues and include your minimal
example?

 -Marius

On Dec 23, 2024, at 15:45, Steve Lelievre via Discuss
discuss@lists.openscad.org wrote:

Hi,

Further testing shows that my problem happens only when I use roof to
define the initial 3D shape, and that it works just fine with roof
method 'straight'. As well, I found a simpler failing case (no hull):

minkowski() {
  scale([1, 1, -15]) roof() circle(d = 15, $fn = 60);
  sphere(d  = 1);
}

The problem can be made to go away by choosing other values for the z
scaling, the circle diameter, or the circle facet number.

Steve

On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote:

Does this only fail when using roof(), or are you able to reproduce
similar behavior also without roof()?

 -Markus

On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss
discuss@lists.openscad.org wrote:

Nightly 2024.12.21 on Windows 10 gives me an error message when
rendering the following code

x = -15;
$fn = 60;
minkowski() {
  scale([1, 1, x]) roof() hull() {
    circle(d = 15);
    translate([0, 6]) circle(d = 6);
  }
  sphere(d = 0.06);
}

The message produced is

WARNING: [manifold] Minkowski failed with error, falling back to
Nef operation: CGAL ERROR: assertion violation!
Expr: e->incident_sface() != SFace_const_handle()
File:
/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 329
ERROR: The given mesh is not closed! Unable to convert to
CGAL_Nef_Polyhedron.

I can circumvent the problem by using x = +15 and inverting the
resulting shape by adding "scale([1,1,-1])" just  before the
minkowski. The issue can also be removed by reducing the value of
$fn to 28 or less.

Although I can avoid the issue, I'd be interested to hear an
explanation of the cause - in particular why it works okay for x =
+15 but not x = -15 (to me, it's just symmetry so sign inversion
should not make a difference.)

Cheers,

Steve


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

--
https://www.gnomoni.ca
https://www.youtube.com/@gnomonica


OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org


OpenSCAD mailing list
To unsubscribe send an email todiscuss-leave@lists.openscad.org

Issue #5528 On 2024-12-23 1:09 p.m., Marius Kintel via Discuss wrote: > Thanks for confirming. This could be a bug in roof(); roof is still > very experimental and have some rough corners. > Could you open an issue on > https://github.com/openscad/openscad/issues and include your minimal > example? > >  -Marius > >> On Dec 23, 2024, at 15:45, Steve Lelievre via Discuss >> <discuss@lists.openscad.org> wrote: >> >> Hi, >> >> Further testing shows that my problem happens only when I use roof to >> define the initial 3D shape, and that it works just fine with roof >> method 'straight'. As well, I found a simpler failing case (no hull): >> >> minkowski() { >>   scale([1, 1, -15]) roof() circle(d = 15, $fn = 60); >>   sphere(d  = 1); >> } >> >> The problem can be made to go away by choosing other values for the z >> scaling, the circle diameter, or the circle facet number. >> >> Steve >> >> >> >> >> On 2024-12-23 8:44 a.m., Marius Kintel via Discuss wrote: >>> Does this only fail when using roof(), or are you able to reproduce >>> similar behavior also without roof()? >>> >>>  -Markus >>> >>>> On Dec 23, 2024, at 10:48, Steve Lelievre via Discuss >>>> <discuss@lists.openscad.org> wrote: >>>> >>>> Nightly 2024.12.21 on Windows 10 gives me an error message when >>>> rendering the following code >>>> >>>> x = -15; >>>> $fn = 60; >>>> minkowski() { >>>>   scale([1, 1, x]) roof() hull() { >>>>     circle(d = 15); >>>>     translate([0, 6]) circle(d = 6); >>>>   } >>>>   sphere(d = 0.06); >>>> } >>>> >>>> >>>> The message produced is >>>> >>>> WARNING: [manifold] Minkowski failed with error, falling back to >>>> Nef operation: CGAL ERROR: assertion violation! >>>> Expr: e->incident_sface() != SFace_const_handle() >>>> File: >>>> /mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h >>>> Line: 329 >>>> ERROR: The given mesh is not closed! Unable to convert to >>>> CGAL_Nef_Polyhedron. >>>> >>>> I can circumvent the problem by using x = +15 and inverting the >>>> resulting shape by adding "scale([1,1,-1])" just  before the >>>> minkowski. The issue can also be removed by reducing the value of >>>> $fn to 28 or less. >>>> >>>> Although I can avoid the issue, I'd be interested to hear an >>>> explanation of the cause - in particular why it works okay for x = >>>> +15 but not x = -15 (to me, it's just symmetry so sign inversion >>>> should not make a difference.) >>>> >>>> >>>> Cheers, >>>> >>>> Steve >>>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> To unsubscribe send an email to discuss-leave@lists.openscad.org >>> _______________________________________________ >>> OpenSCAD mailing list >>> To unsubscribe send an email to discuss-leave@lists.openscad.org >> >> -- >> https://www.gnomoni.ca >> https://www.youtube.com/@gnomonica >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org > > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email todiscuss-leave@lists.openscad.org -- https://www.gnomoni.ca https://www.youtube.com/@gnomonica