simplest i can think of doing this in purely openSCAD is with following
code:

include<dependencies2.scad>

path=[for(t=[0:360])
[10cos(2t)(3+cos(5t)),
10sin(2t)(3+cos(5t)),
10sin(5t) ]];

p_line3dc(path,8);

you would need the file dependencies2.scad for the same (attached here)

On Sat, 27 May 2023 at 18:07, terrypingm@gmail.com terrypingm@gmail.com
wrote:

On Sat, May 27, 2023 at 01:36:39PM +0100, terrypingm@gmail.com wrote:

My code is 400 times smaller (*):

d = 10;

R = 27;
rr = 10;
n = 5;

module onesphere (t)
{
r = R + rrsin (n360t);
x = r * sin (t * 2 * 360);
y = r * cos (t * 2 * 360);
z = rr * cos (n360*t);
translate ([x,y,z]) sphere (d=d);
}

step=0.005;

for (t = [0:step:1]) {
hull () {
onesphere (t);
onesphere (t+step);
}
}

(less typing, i'd say :-) )

(Try n=3, 7, and 9 too! )

Roger.

(*) Measured BEFORE I made it generic for n=...)

--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110 **
**    Delftechpark 11 2628 XJ  Delft, The Netherlands.  KVK: 27239233    **
f equals m times a. When your f is steady, and your m is going down
your a is going up.  -- Chris Hadfield about flying up the space shuttle.

hull is not very neat in this case

for finer models you would need some modules like path_extrude, which
extrudes the circular section along the path.

long back i wrote this function which is in the file dependencies.scad
now mostly i work in python
if you try that, it would be a very smooth knot:

include<dependencies.scad>

path=[for(t=[0:359])
[10cos(2t)(3+cos(5t)),
10sin(2t)(3+cos(5t)),
10sin(5t) ]];

sec=circle(4);

sol=path_extrudec(sec,path); // extrudec means closed extrusion
swp(sol); // module to render the extruded solid "sweep"

On Sat, 27 May 2023 at 18:27, Rogier Wolff R.E.Wolff@bitwizard.nl wrote:

It would be really interesting to see an example, which shows how this
knot is made using the turtle library from BOSL2

Karl

Am 27.05.23 um 13:45 schrieb Sanjeev Prabhakar:

Also try this another interesting trefoil knot

include<dependencies.scad>

path=[for(t=[0:359])
[10*(sin(t)+2sin(2t)),
10*(cos(t)-2cos(2t)),
-10sin(3t)]];

sec=circle(4);

sol=path_extrudec(sec,path);
swp(sol);

On Sat, 27 May 2023 at 19:00, Sanjeev Prabhakar sprabhakar2006@gmail.com
wrote:

On Sat, 2023-05-27 at 19:07 +0530, Sanjeev Prabhakar wrote:

Where would I find dependencies.scad?

You can download it from here:

https://github.com/sprabhakar2006/openSCAD/

On Sat, 27 May, 2023, 8:53 pm larry, lar3ry@sasktel.net wrote:

The turtle function in BOSL2 is meant for creating shapes that are
irregular in form.  This shape has a tidy mathematical definition, so using
turtle does not make sense.  If you want to do it in BOSL2, I'd suggest the
code below.  It's about 50x faster than the code posted by Rogier---10s for
Rogier's code vs 0.2s for the BOSL2 code.  Perhaps lazy unions would help
Rogier's code run faster---I didn't check.  I also think that the
polyhedron approach used in BOSL2 produces a better looking model.

include<BOSL2/std.scad>
$fn=32;

d = 10;
R = 27;
rr = 10;
n = 5;
step=0.005;

function onept(t) =
let(
r = R + rrsin (n360t),
x = r * sin (t * 2 * 360),
y = r * cos (t * 2 * 360),
z = rr * cos (n360*t)
)
[x,y,z];

path = [for(t=[0:step:1]) onept(t)];

path_sweep(circle(d=d), path);

On Sat, May 27, 2023 at 9:34 AM Karl Exler karl.exler@meinklang.cc wrote: