OpenSCAD general discussion Mailing-list

### simple question

JB
Jon Bondy
Tue, Jul 2, 2024 2:13 AM

I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

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I'm sure I will be embarrassed at how simple this is, but. Given two polygons with equal number of points, but slightly different shape, how can I make a solid with one on the bottom and the other on the top.  I tried hull(), but the shapes have concavities which hull() destroys. It feels like it is a very simple (almost trivial) skin() Jon -- This email has been checked for viruses by AVG antivirus software. www.avg.com
DP
David Phillip Oster
Tue, Jul 2, 2024 2:29 AM

I use a function that given, a list of 2D points, a polygon, returns a list
of 3 d points, where the Z coordinate is a constant or the result of a
simple function.

I have a function that, given two such lists of 3D points, marches around
the lists, using a pair from list A, and a pair from list B, generating the
edge list that polyhedron() needs, then it appends the polygons-in-3space
as end caps, making a valid OpenSCAD polyhedron.

This kind of thing (not exactly what you want, but close.):

``````// Schwarz Lantern https://www.youtube.com/watch?v=yAEveAH2KwI

// by David Phillip Oster 12/27/2023

// Creates a generalized cylinder by lacing up with triangles

// parallel bands, each with the same number of vertices.

// In this example, the vertices in each band are equi-spaced along
``````

circles, each the same size

``````// but they could be almost a series of almost any shape as long as the
``````

vertices line up.

``````// number of bands

b=14; // [1:20]

// number of vertices

p=3; // [3:20]

// height in mm

h = 100;

// diameter in mm

d = 100;

// vertices: each band is offset from the previous by half the distance
``````

between vertices

``````pts = [for(y=[0:b], i=[0:p-1]) [(d/2)*sin(360*(i + (y%2)/2)/p),
``````

(d/2)cos(360(i + (y%2)/2)/p), y*h/b]];

``````// indices of top face

top = [for(i=[p-1:-1:0]) i];

// indices of bottom face

bottom = [for(i=[p-1:-1:0]) len(pts) - i - 1];

// walls are 0,1 from bottom, 1, from top, then advance both by 1,
``````

modulo len.

``````walls0 = [for(y=[0:b-1], i=[0:p-1]) let(off=y*p,
``````

inc=(y%2)?1:0)[off+(i%p),  off+(i+1)%p,  off+p+((i+inc)%p)] ];

``````walls1 = [for(y=[0:b-1], i=[0:p-1]) let(off=y*p,
``````

inc=(y%2)?p:1)[off+p+(i%p), off+(i+inc)%p, off+p+((i+1)%p)] ];

``````// Concatenate two lists.

function cat(L1, L2) = [for(L=[L1, L2], a=L) a];

polyhedron(points=pts, faces= cat(cat([top, bottom], walls0), walls1) );
``````

On Mon, Jul 1, 2024 at 7:13 PM Jon Bondy via Discuss <

I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

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

I use a function that given, a list of 2D points, a polygon, returns a list of 3 d points, where the Z coordinate is a constant or the result of a simple function. I have a function that, given two such lists of 3D points, marches around the lists, using a pair from list A, and a pair from list B, generating the edge list that polyhedron() needs, then it appends the polygons-in-3space as end caps, making a valid OpenSCAD polyhedron. This kind of thing (not exactly what you want, but close.): // Schwarz Lantern https://www.youtube.com/watch?v=yAEveAH2KwI // by David Phillip Oster 12/27/2023 // Creates a generalized cylinder by lacing up with triangles // parallel bands, each with the same number of vertices. // In this example, the vertices in each band are equi-spaced along circles, each the same size // but they could be almost a series of almost any shape as long as the vertices line up. // number of bands b=14; // [1:20] // number of vertices p=3; // [3:20] // height in mm h = 100; // diameter in mm d = 100; // vertices: each band is offset from the previous by half the distance between vertices pts = [for(y=[0:b], i=[0:p-1]) [(d/2)*sin(360*(i + (y%2)/2)/p), (d/2)*cos(360*(i + (y%2)/2)/p), y*h/b]]; // indices of top face top = [for(i=[p-1:-1:0]) i]; // indices of bottom face bottom = [for(i=[p-1:-1:0]) len(pts) - i - 1]; // walls are 0,1 from bottom, 1, from top, then advance both by 1, modulo len. walls0 = [for(y=[0:b-1], i=[0:p-1]) let(off=y*p, inc=(y%2)?1:0)[off+(i%p), off+(i+1)%p, off+p+((i+inc)%p)] ]; walls1 = [for(y=[0:b-1], i=[0:p-1]) let(off=y*p, inc=(y%2)?p:1)[off+p+(i%p), off+(i+inc)%p, off+p+((i+1)%p)] ]; // Concatenate two lists. function cat(L1, L2) = [for(L=[L1, L2], a=L) a]; polyhedron(points=pts, faces= cat(cat([top, bottom], walls0), walls1) ); On Mon, Jul 1, 2024 at 7:13 PM Jon Bondy via Discuss < discuss@lists.openscad.org> wrote: > I'm sure I will be embarrassed at how simple this is, but. > > Given two polygons with equal number of points, but slightly different > shape, how can I make a solid with one on the bottom and the other on > the top. I tried hull(), but the shapes have concavities which hull() > destroys. > > It feels like it is a very simple (almost trivial) skin() > > Jon > > > -- > This email has been checked for viruses by AVG antivirus software. > www.avg.com > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
SP
Sanjeev Prabhakar
Tue, Jul 2, 2024 3:26 AM

dont be embarrased, its not so simple at all.

I wrote a function which can do this.

here is the function with an example

function faces(sol)=

//    calculate the faces for the vertices with shape l x m with first and
the last end closed
let(
l=len(sol),
m=len(sol[0]),
n1=[for(i=[0:m-1])i],
n2=[for(i=[0:l-2]) each ([ for(j=[0:m-1])
each
j<m-1?[[(j+1)+im,j+im,j+(i+1)m],[(j+1)+im,j+(i+1)m,(j+1)+(i+1)m]]:
[[0+i
m,j+i
m,j+(i+1)m],[0+im,j+(i+1)*m,0+(i+1)*m]]
])],
n3=[for(i=[0:m-1])i+(l-1)*m],
n4=[for(i=[len(n3)-1:-1:0])n3[i]],
n=[n1,each (n2),n4]
)n;

function vertices(sol)=
[each for (p=sol)p];

// module for rendering the polyhedron with ends closed
module swp(sol){
let(
v1=vertices(sol),
f1=faces(sol)
)
polyhedron(v1,f1,convexity=10);

}

r=10;
r1=8;
r2=5;
n=10;
a=[for(i=[-360/n/4:360/n/2:360]) [rcos(i),rsin(i),0] ];
b=[for(i=[0:360/n:360])[r1cos(i),r1sin(i)]];
c=[for(i=[360/n/2:360/n:360+360/n])[r2cos(i),r2sin(i)]];
d=[for(i=[0:len(b)-1])each([[b[i].x,b[i].y,10],[c[i].x,c[i].y,10]])];

swp([a,d]);

On Tue, 2 Jul 2024 at 07:43, Jon Bondy via Discuss <

I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

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

dont be embarrased, its not so simple at all. I wrote a function which can do this. here is the function with an example function faces(sol)= // calculate the faces for the vertices with shape l x m with first and the last end closed let( l=len(sol), m=len(sol[0]), n1=[for(i=[0:m-1])i], n2=[for(i=[0:l-2]) each ([ for(j=[0:m-1]) each j<m-1?[[(j+1)+i*m,j+i*m,j+(i+1)*m],[(j+1)+i*m,j+(i+1)*m,(j+1)+(i+1)*m]]: [[0+i*m,j+i*m,j+(i+1)*m],[0+i*m,j+(i+1)*m,0+(i+1)*m]] ])], n3=[for(i=[0:m-1])i+(l-1)*m], n4=[for(i=[len(n3)-1:-1:0])n3[i]], n=[n1,each (n2),n4] )n; function vertices(sol)= [each for (p=sol)p]; // module for rendering the polyhedron with ends closed module swp(sol){ let( v1=vertices(sol), f1=faces(sol) ) polyhedron(v1,f1,convexity=10); } r=10; r1=8; r2=5; n=10; a=[for(i=[-360/n/4:360/n/2:360]) [r*cos(i),r*sin(i),0] ]; b=[for(i=[0:360/n:360])[r1*cos(i),r1*sin(i)]]; c=[for(i=[360/n/2:360/n:360+360/n])[r2*cos(i),r2*sin(i)]]; d=[for(i=[0:len(b)-1])each([[b[i].x,b[i].y,10],[c[i].x,c[i].y,10]])]; swp([a,d]); On Tue, 2 Jul 2024 at 07:43, Jon Bondy via Discuss < discuss@lists.openscad.org> wrote: > I'm sure I will be embarrassed at how simple this is, but. > > Given two polygons with equal number of points, but slightly different > shape, how can I make a solid with one on the bottom and the other on > the top. I tried hull(), but the shapes have concavities which hull() > destroys. > > It feels like it is a very simple (almost trivial) skin() > > Jon > > > -- > This email has been checked for viruses by AVG antivirus software. > www.avg.com > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
AM
Tue, Jul 2, 2024 4:02 AM

You have to use polyhedron() to do that.  I personally think that using
polyhedron() directly is a recipe for frustration and wasted time.  Use a
library.  BOSL2 has vnf_vertex_array() and skin() that can do this.  They
will both do exactly what you want.  The skin() function can help if the
vertices aren't indexed into the best alignment between the polygons, and
does also attempt to address the case where the vertex count of the two
polygons is not the same.

On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss <

I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

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

You have to use polyhedron() to do that. I personally think that using polyhedron() directly is a recipe for frustration and wasted time. Use a library. BOSL2 has vnf_vertex_array() and skin() that can do this. They will both do exactly what you want. The skin() function can help if the vertices aren't indexed into the best alignment between the polygons, and does also attempt to address the case where the vertex count of the two polygons is not the same. On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss < discuss@lists.openscad.org> wrote: > I'm sure I will be embarrassed at how simple this is, but. > > Given two polygons with equal number of points, but slightly different > shape, how can I make a solid with one on the bottom and the other on > the top. I tried hull(), but the shapes have concavities which hull() > destroys. > > It feels like it is a very simple (almost trivial) skin() > > Jon > > > -- > This email has been checked for viruses by AVG antivirus software. > www.avg.com > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
JB
Jon Bondy
Tue, Jul 2, 2024 11:07 AM

Thank you.  Is there any chance that BOSL2 over-rides the native
offset() function?  I am now getting error messages for offset(). I
could not find an offset() defined in BOSL2.  Puzzling.

Jon

On 7/2/2024 12:02 AM, Adrian Mariano via Discuss wrote:

You have to use polyhedron() to do that.  I personally think that
using polyhedron() directly is a recipe for frustration and wasted
time.  Use a library.  BOSL2 has vnf_vertex_array() and skin() that
can do this.  They will both do exactly what you want.   The skin()
function can help if the vertices aren't indexed into the best
alignment between the polygons, and does also attempt to address the
case where the vertex count of the two polygons is not the same.

On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss

`````` I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly
different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which
hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com <http://www.avg.com>
_______________________________________________
To unsubscribe send an email to discuss-leave@lists.openscad.org
``````

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

Adrian: Thank you.  Is there any chance that BOSL2 over-rides the native offset() function?  I am now getting error messages for offset(). I could not find an offset() defined in BOSL2.  Puzzling. Jon On 7/2/2024 12:02 AM, Adrian Mariano via Discuss wrote: > You have to use polyhedron() to do that.  I personally think that > using polyhedron() directly is a recipe for frustration and wasted > time.  Use a library.  BOSL2 has vnf_vertex_array() and skin() that > can do this.  They will both do exactly what you want.   The skin() > function can help if the vertices aren't indexed into the best > alignment between the polygons, and does also attempt to address the > case where the vertex count of the two polygons is not the same. > > On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss > <discuss@lists.openscad.org> wrote: > > I'm sure I will be embarrassed at how simple this is, but. > > Given two polygons with equal number of points, but slightly > different > shape, how can I make a solid with one on the bottom and the other on > the top.  I tried hull(), but the shapes have concavities which > hull() > destroys. > > It feels like it is a very simple (almost trivial) skin() > > Jon > > > -- > This email has been checked for viruses by AVG antivirus software. > www.avg.com <http://www.avg.com> > _______________________________________________ > 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
JJ
jon jonbondy.com
Tue, Jul 2, 2024 11:18 AM

Never mind.  It is not the offset().  The documentation for skin() says it takes a "profile", but I gather that a polygon() is not a profile:

module Shape()
skin(
[
//        offset(4)
//            offset(-4)
polygon([
[0, 0],                                                // 1
[9.4, 0],                                            // 2
[9.4 + 4.1                  , -9.4],                // 3
[9.4 + 4.1 + 21.3            , -9.4],                // 4
[9.4 + 4.1 + 21.3 + 4.1      , 0],                    // 5
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 0],                    // 6
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 28.5],                // 7
[9.4 + 4.1 + 21.3 + 4.1      , 28.5],                // 8
[9.4 + 4.1 + 21.3            , 28.5 + 9.4],            // 9
[9.4 + 4.1                  , 28.5 + 9.4],            // 10
[9.4                        , 28.5],                // 11
[0                          , 28.5]                // 12
]),
//        offset(4)
//            offset(-4)
polygon([
[0, 0],                                                // 1
[9.4, 0],                                            // 2
[9.4 + 4.1                  , -9.4],                // 3
[9.4 + 4.1 + 21.3            , -9.4],                // 4
[9.4 + 4.1 + 21.3 + 4.1      , 0],                    // 5
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 0],                    // 6
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 33.1],                // 7
[9.4 + 4.1 + 21.3 + 4.1      , 33.1],                // 8
[9.4 + 4.1 + 21.3            , 33.1 + 9.4],            // 9
[9.4 + 4.1                  , 33.1 + 9.4],            // 10
[9.4                        , 33.1],                // 11
[0                          , 33.1]                // 12
])
], z = [0, 36.3], slices=2);

!Shape();

On 7/2/2024 7:07 AM, Jon Bondy via Discuss wrote:

Thank you.  Is there any chance that BOSL2 over-rides the native offset() function?  I am now getting error messages for offset().  I could not find an offset() defined in BOSL2.  Puzzling.

Jon

On 7/2/2024 12:02 AM, Adrian Mariano via Discuss wrote:
You have to use polyhedron() to do that.  I personally think that using polyhedron() directly is a recipe for frustration and wasted time.  Use a library.  BOSL2 has vnf_vertex_array() and skin() that can do this.  They will both do exactly what you want.  The skin() function can help if the vertices aren't indexed into the best alignment between the polygons, and does also attempt to address the case where the vertex count of the two polygons is not the same.

On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss <discuss@lists.openscad.orgmailto:discuss@lists.openscad.org> wrote:
I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
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To unsubscribe send an email to discuss-leave@lists.openscad.orgmailto:discuss-leave@lists.openscad.org

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JJ
jon jonbondy.com
Tue, Jul 2, 2024 11:55 AM

Never mind, again.  Removing the polygon() and just using the point list works.

Sorry for all of the flailing.

Jon

On 7/2/2024 7:18 AM, jon jonbondy.com via Discuss wrote:

Never mind.  It is not the offset().  The documentation for skin() says it takes a "profile", but I gather that a polygon() is not a profile:

module Shape()
skin(
[
//        offset(4)
//            offset(-4)
polygon([
[0, 0],                                                // 1
[9.4, 0],                                            // 2
[9.4 + 4.1                  , -9.4],                // 3
[9.4 + 4.1 + 21.3            , -9.4],                // 4
[9.4 + 4.1 + 21.3 + 4.1      , 0],                    // 5
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 0],                    // 6
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 28.5],                // 7
[9.4 + 4.1 + 21.3 + 4.1      , 28.5],                // 8
[9.4 + 4.1 + 21.3            , 28.5 + 9.4],            // 9
[9.4 + 4.1                  , 28.5 + 9.4],            // 10
[9.4                        , 28.5],                // 11
[0                          , 28.5]                // 12
]),
//        offset(4)
//            offset(-4)
polygon([
[0, 0],                                                // 1
[9.4, 0],                                            // 2
[9.4 + 4.1                  , -9.4],                // 3
[9.4 + 4.1 + 21.3            , -9.4],                // 4
[9.4 + 4.1 + 21.3 + 4.1      , 0],                    // 5
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 0],                    // 6
[9.4 + 4.1 + 21.3 + 4.1 + 9.4, 33.1],                // 7
[9.4 + 4.1 + 21.3 + 4.1      , 33.1],                // 8
[9.4 + 4.1 + 21.3            , 33.1 + 9.4],            // 9
[9.4 + 4.1                  , 33.1 + 9.4],            // 10
[9.4                        , 33.1],                // 11
[0                          , 33.1]                // 12
])
], z = [0, 36.3], slices=2);

!Shape();

On 7/2/2024 7:07 AM, Jon Bondy via Discuss wrote:

Thank you.  Is there any chance that BOSL2 over-rides the native offset() function?  I am now getting error messages for offset().  I could not find an offset() defined in BOSL2.  Puzzling.

Jon

On 7/2/2024 12:02 AM, Adrian Mariano via Discuss wrote:
You have to use polyhedron() to do that.  I personally think that using polyhedron() directly is a recipe for frustration and wasted time.  Use a library.  BOSL2 has vnf_vertex_array() and skin() that can do this.  They will both do exactly what you want.  The skin() function can help if the vertices aren't indexed into the best alignment between the polygons, and does also attempt to address the case where the vertex count of the two polygons is not the same.

On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss <discuss@lists.openscad.orgmailto:discuss@lists.openscad.org> wrote:
I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

--
This email has been checked for viruses by AVG antivirus software.
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To unsubscribe send an email to discuss-leave@lists.openscad.orgmailto:discuss-leave@lists.openscad.org

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AM
Tue, Jul 2, 2024 12:26 PM

There is no offset() function in native OpenSCAD, only the offset()
module.  BOSL2 supplies the offset() function, which you'll want to use
(with closed=true), but does not change the module.  It looks like you
have the same point list, differently offset.  You generally only need
slices>0 if there is twisting, so you might check if the larger value makes
a different.  (If it does, 2 is probably not large enough.)

On Tue, Jul 2, 2024 at 7:07 AM Jon Bondy jon@jonbondy.com wrote:

Thank you.  Is there any chance that BOSL2 over-rides the native offset()
function?  I am now getting error messages for offset().  I could not find
an offset() defined in BOSL2.  Puzzling.

Jon
On 7/2/2024 12:02 AM, Adrian Mariano via Discuss wrote:

You have to use polyhedron() to do that.  I personally think that using
polyhedron() directly is a recipe for frustration and wasted time.  Use a
library.  BOSL2 has vnf_vertex_array() and skin() that can do this.  They
will both do exactly what you want.  The skin() function can help if the
vertices aren't indexed into the best alignment between the polygons, and
does also attempt to address the case where the vertex count of the two
polygons is not the same.

On Mon, Jul 1, 2024 at 10:13 PM Jon Bondy via Discuss <

I'm sure I will be embarrassed at how simple this is, but.

Given two polygons with equal number of points, but slightly different
shape, how can I make a solid with one on the bottom and the other on
the top.  I tried hull(), but the shapes have concavities which hull()
destroys.

It feels like it is a very simple (almost trivial) skin()

Jon

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JJ
jon jonbondy.com
Tue, Jul 2, 2024 1:06 PM

I got there, eventually, after a LOT of flailing.  Clearly, I do not understand the difference between a list of numbers, a function() that returns a list of numbers, a module() that returns a list of numbers, and the result of applying polygon() or offset() to any of the above.  It took a lot of trial-and-error to get what I wanted, all attributable to my lack of understanding the representations under the hood for each of these objects.

Jon

On 7/2/2024 8:26 AM, Adrian Mariano wrote:
There is no offset() function in native OpenSCAD, only the offset() module.  BOSL2 supplies the offset() function, which you'll want to use (with closed=true), but does not change the module.  It looks like you have the same point list, differently offset.  You generally only need slices>0 if there is twisting, so you might check if the larger value makes a different.  (If it does, 2 is probably not large enough.)

I got there, eventually, after a LOT of flailing. Clearly, I do not understand the difference between a list of numbers, a function() that returns a list of numbers, a module() that returns a list of numbers, and the result of applying polygon() or offset() to any of the above. It took a lot of trial-and-error to get what I wanted, all attributable to my lack of understanding the representations under the hood for each of these objects. Jon On 7/2/2024 8:26 AM, Adrian Mariano wrote: There is no offset() function in native OpenSCAD, only the offset() module. BOSL2 supplies the offset() function, which you'll want to use (with closed=true), but does not change the module. It looks like you have the same point list, differently offset. You generally only need slices>0 if there is twisting, so you might check if the larger value makes a different. (If it does, 2 is probably not large enough.)
L
larry
Tue, Jul 2, 2024 4:58 PM

On Tue, 2024-07-02 at 13:06 +0000, jon jonbondy.com via Discuss wrote:

I got there, eventually, after a LOT of flailing.  Clearly, I do not
understand the difference between a list of numbers, a function()
that returns a list of numbers, a module() that returns a list of
numbers, and the result of applying polygon() or offset() to any of
the above.  It took a lot of trial-and-error to get what I wanted,
all attributable to my lack of understanding the representations
under the hood for each of these objects.
Jon

I'd be interested in the final code, if you are willing to share it.

On 7/2/2024 8:26 AM, Adrian Mariano wrote:

There is no offset() function in native OpenSCAD, only the offset()
module.  BOSL2 supplies the offset() function, which you'll want to
use (with closed=true), but does not change the module.   It looks
like you have the same point list, differently offset.  You
generally only need slices>0 if there is twisting, so you might
check if the larger value makes a different.  (If it does, 2 is
probably not large enough.)