### New and a question

D
disruptivesolutionsnl@gmail.com
Fri, Jul 2, 2021 2:26 PM

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the "lines" between them is not
equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,

Ben

Hello, I am new to his forum/mailing list, so thank you for having me! I want to make an octagonal shape (8 sides) where I could change the angle of each corner, so the lengths of the "lines" between them is not equivalent. How could I do this? I hope my question is clear enough without presenting an example picture. With kind regards, Ben
MM
Michael Möller
Fri, Jul 2, 2021 2:30 PM

That is just a regular polyhedron, with 8 points.

You just need the list of xy points. This is a 2D shape, so remember to
extrude it.

Msquare

On Fri, 2 Jul 2021 at 16:26, disruptivesolutionsnl@gmail.com wrote:

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the “lines” between them is not
equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,

Ben

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

That is just a regular polyhedron, with 8 points. https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#polygon You just need the list of xy points. This is a 2D shape, so remember to extrude it. Msquare On Fri, 2 Jul 2021 at 16:26, <disruptivesolutionsnl@gmail.com> wrote: > Hello, > > > > I am new to his forum/mailing list, so thank you for having me! > > > > I want to make an octagonal shape (8 sides) where I could change the angle > of each corner, so the lengths of the “lines” between them is not > equivalent. How could I do this? > > > > I hope my question is clear enough without presenting an example picture. > > > > With kind regards, > > Ben > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
NH
Fri, Jul 2, 2021 2:33 PM

You can make an arbitrary 8 sided shape by giving a list of vertices to
polygon(). If you want to specify the angles you would need to use some
trigonometry to work out the vertex positions, or perhaps use a library
with turtle mode paths.

On Fri, 2 Jul 2021 at 15:26, disruptivesolutionsnl@gmail.com wrote:

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the “lines” between them is not
equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,

Ben

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

You can make an arbitrary 8 sided shape by giving a list of vertices to polygon(). If you want to specify the angles you would need to use some trigonometry to work out the vertex positions, or perhaps use a library with turtle mode paths. On Fri, 2 Jul 2021 at 15:26, <disruptivesolutionsnl@gmail.com> wrote: > Hello, > > > > I am new to his forum/mailing list, so thank you for having me! > > > > I want to make an octagonal shape (8 sides) where I could change the angle > of each corner, so the lengths of the “lines” between them is not > equivalent. How could I do this? > > > > I hope my question is clear enough without presenting an example picture. > > > > With kind regards, > > Ben > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
T
Terry
Fri, Jul 2, 2021 7:26 PM

On Fri, 2 Jul 2021 16:26:09 +0200, you wrote:

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the "lines" between them is not
equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,

Ben

On Fri, 2 Jul 2021 16:26:09 +0200, you wrote:

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the "lines" between them is not
equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,

Ben

Hi Ben,

I'm newish here too, and an OS novice, but one of the books I've bought
has some examples from which I've extracted the following. Although it's
not a close match, with a revised function it might be a start.

module triangle(p1,p2,p3) {
polygon([p1,p2,p3]);
}

for(n=[0:poly_edges-1]) {
triangle([0,0],p1,p2);
}
}

// Octagon example
poly_edges = 8;
poly_height = 3;
linear_extrude(poly_height)

On Fri, 2 Jul 2021 16:26:09 +0200, you wrote: >Hello, > > > >I am new to his forum/mailing list, so thank you for having me! > > > >I want to make an octagonal shape (8 sides) where I could change the angle >of each corner, so the lengths of the "lines" between them is not >equivalent. How could I do this? > > > >I hope my question is clear enough without presenting an example picture. > > > >With kind regards, > >Ben On Fri, 2 Jul 2021 16:26:09 +0200, you wrote: >Hello, > > > >I am new to his forum/mailing list, so thank you for having me! > > > >I want to make an octagonal shape (8 sides) where I could change the angle >of each corner, so the lengths of the "lines" between them is not >equivalent. How could I do this? > > > >I hope my question is clear enough without presenting an example picture. > > > >With kind regards, > >Ben Hi Ben, I'm newish here too, and an OS novice, but one of the books I've bought has some examples from which I've extracted the following. Although it's not a close match, with a revised function it might be a start. function cartesian(radius,angle)= [radius*cos(angle),radius*sin(angle)]; module triangle(p1,p2,p3) { polygon([p1,p2,p3]); } module regular_polygon(poly_edges,poly_radius) { for(n=[0:poly_edges-1]) { p1 = cartesian(poly_radius,n*360/poly_edges); p2 = cartesian(poly_radius,(n+1)*360/poly_edges); triangle([0,0],p1,p2); } } // Octagon example poly_edges = 8; poly_radius = 20; poly_height = 3; linear_extrude(poly_height) regular_polygon(poly_edges,poly_radius);
T
Terry
Fri, Jul 2, 2021 7:36 PM

It's odd that my post is accessible in the forum but I haven't yet
received it as an email. Anyway, in the forum somehow the pasted code
has been corrupted (as you see from the accompanying screenshot.
Hopefully the email will be correct. Here's another paste:

module triangle(p1,p2,p3) {
polygon([p1,p2,p3]);
}

for(n=[0:poly_edges-1]) {
triangle([0,0],p1,p2);
}
}

// Octagon example
poly_edges = 8;
poly_height = 3;
linear_extrude(poly_height)

It's odd that my post is accessible in the forum but I haven't yet received it as an email. Anyway, in the forum somehow the pasted code has been corrupted (as you see from the accompanying screenshot. Hopefully the email will be correct. Here's another paste: function cartesian(radius,angle)= [radius*cos(angle),radius*sin(angle)]; module triangle(p1,p2,p3) { polygon([p1,p2,p3]); } module regular_polygon(poly_edges,poly_radius) { for(n=[0:poly_edges-1]) { p1 = cartesian(poly_radius,n*360/poly_edges); p2 = cartesian(poly_radius,(n+1)*360/poly_edges); triangle([0,0],p1,p2); } } // Octagon example poly_edges = 8; poly_radius = 20; poly_height = 3; linear_extrude(poly_height) regular_polygon(poly_edges,poly_radius);
JB
Jordan Brown
Fri, Jul 2, 2021 8:10 PM

It's not super-obvious, but OpenSCAD has a built-in way to do this:

``````circle(r=poly_radius, \$fn=poly_edges);
``````

Note that OpenSCAD measures the "radius" of the polygon from the center
to the vertices.

``````function adjustr(r, n) = r / cos(360/n/2);
``````

\$fn=n) will give you a polygon where "r" is the distance from the center
to the middle of the edges.

Also note that OpenSCAD circle() behavior puts one vertex at [r, 0], so
that a square ends up diamond-oriented.  That's not wrong, but sometimes
it's more convenient to have an edge there.  For that, you want

``````rotate(360/n/2) circle(...);
``````

If you combine those:

``````rotate(360/n/2) circle(r=adjustr(r, n), \$fn=n);
``````

then you end up with a polygon where one edge is aligned with the Y axis
and has its center at [r, 0].  If the number of sides is even, another
Y-aligned edge is at [-r,0], and if it's divisible by four then there
will be X-aligned edges at [0,r] and [0,-r].

JB
Jordan Brown
Fri, Jul 2, 2021 8:24 PM

On 7/2/2021 1:10 PM, Jordan Brown wrote:

`````` rotate(360/n/2) circle(r=adjustr(r, n), \$fn=n);
``````

Perhaps circle (and cylinder and sphere) should get additional options
so that these adjustments are built in, rather than everybody needing to

For the radius adjustment, there could be "ir", "or", "id", and "od"
parameters. "or" and "od" would be aliases for the current "r" and "d"
and specify to-vertex dimensions, while "ir" and "id" would specify
to-edge dimensions.

I don't know about the rotation adjustment, but perhaps it would be a
boolean or perhaps it would be an "align" parameter with options
"vertex" and "edge".

It's hard to tell when adding these small tweaks to the base (thus
cluttering the base more) is a win over having people or libraries
invent new names for new operations that are almost the same as the
existing operations.

On 7/2/2021 1:10 PM, Jordan Brown wrote: > > rotate(360/n/2) circle(r=adjustr(r, n), \$fn=n); > Perhaps circle (and cylinder and sphere) should get additional options so that these adjustments are built in, rather than everybody needing to layer adjustments on top. For the radius adjustment, there could be "ir", "or", "id", and "od" parameters. "or" and "od" would be aliases for the current "r" and "d" and specify to-vertex dimensions, while "ir" and "id" would specify to-edge dimensions. I don't know about the rotation adjustment, but perhaps it would be a boolean or perhaps it would be an "align" parameter with options "vertex" and "edge". It's hard to tell when adding these small tweaks to the base (thus cluttering the base more) is a win over having people or libraries invent new names for new operations that are almost the same as the existing operations.
DG
David Gustavson
Fri, Jul 2, 2021 8:36 PM

It’s because you use Gmail.
Gmail has a policy that it will never show you an email that it can tell was sent by yourself.
Makes me crazy when testing groups.
I guess they think it would insult your memory?

--
David Gustavson
dbg@SCIzzL.com

On Fri, Jul 2, 2021, at 12:36 PM, Terry wrote:

It's odd that my post is accessible in the forum but I haven't yet
received it as an email. Anyway, in the forum somehow the pasted code
has been corrupted (as you see from the accompanying screenshot.
Hopefully the email will be correct. Here's another paste:

module triangle(p1,p2,p3) {
polygon([p1,p2,p3]);
}

for(n=[0:poly_edges-1]) {
triangle([0,0],p1,p2);
}
}

// Octagon example
poly_edges = 8;
poly_height = 3;
linear_extrude(poly_height)

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

RD
Revar Desmera
Fri, Jul 2, 2021 10:58 PM

Something like this?

r=50; sides=8; small_ang=30;
poly = [
for (a=[0:90:359],b=[-0.5,0.5])
let(ang=a+bsmall_ang)
r
[cos(ang), sin(ang)]
]
polygon(poly);

Or do you need specific interior angles on the polygon?

• Revar

On Jul 2, 2021, at 7:26 AM, disruptivesolutionsnl@gmail.com disruptivesolutionsnl@gmail.com wrote:

Hello,

I am new to his forum/mailing list, so thank you for having me!

I want to make an octagonal shape (8 sides) where I could change the angle of each corner, so the lengths of the “lines” between them is not equivalent. How could I do this?

I hope my question is clear enough without presenting an example picture.

With kind regards,
Ben

Something like this? r=50; sides=8; small_ang=30; poly = [ for (a=[0:90:359],b=[-0.5,0.5]) let(ang=a+b*small_ang) r*[cos(ang), sin(ang)] ] polygon(poly); Or do you need specific interior angles on the polygon? - Revar > On Jul 2, 2021, at 7:26 AM, <disruptivesolutionsnl@gmail.com> <disruptivesolutionsnl@gmail.com> wrote: > > Hello, > > I am new to his forum/mailing list, so thank you for having me! > > I want to make an octagonal shape (8 sides) where I could change the angle of each corner, so the lengths of the “lines” between them is not equivalent. How could I do this? > > I hope my question is clear enough without presenting an example picture. > > With kind regards, > Ben > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org <mailto:discuss-leave@lists.openscad.org>
MM
Michael Marx
Sat, Jul 3, 2021 12:49 AM

-----Original Message-----
From: Terry [mailto:terrypingm@gmail.com]
Sent: Sat, 3 Jul 2021 05:26

I'm newish here too, and an OS novice, but one of the books I've bought
has some examples

Terry,

Firstly we do not use OS as an abbreviation for OpenSCAD it gets confused for Operating System,
which is a more common term. What version of the OS are you running?

So what books??

BTW, people have missed the subtlety of the original request; different angles/lengths.

I want to make an octagonal shape (8 sides) where I could change the angle
of each corner, so the lengths of the "lines" between them is not
equivalent. How could I do this?

--
This email has been checked for viruses by AVG.
https://www.avg.com

> -----Original Message----- > From: Terry [mailto:terrypingm@gmail.com] > Sent: Sat, 3 Jul 2021 05:26 > I'm newish here too, and an OS novice, but one of the books I've bought > has some examples Terry, Firstly we do not use OS as an abbreviation for OpenSCAD it gets confused for Operating System, which is a more common term. What version of the OS are you running? So what books?? BTW, people have missed the subtlety of the original request; different angles/lengths. > >I want to make an octagonal shape (8 sides) where I could change the angle > >of each corner, so the lengths of the "lines" between them is not > >equivalent. How could I do this? -- This email has been checked for viruses by AVG. https://www.avg.com