is there an easy way to do this?

classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

is there an easy way to do this?

jon_bondy
Imagine a sphere on which a shape has been drawn.  Let's say it is a
circle.  Now, project that back to the center of the sphere, and you
have a cone (of sorts: the base is on the surface of the sphere, and
thus is not flat).

If the original shape was a square, then the projected shape is a cube
of sorts, one face of which has become a single point at the center of
the sphere.

Is there a simple way to specify the 2D shape and then create the 3D object?

I do not actually want the object: I intend to use the object to cut out
that cross section from a ring (torus).  The whole point is that the
edges of the cutout all point in to the center of the ring/sphere.

Thanks!

Jon


_______________________________________________
OpenSCAD mailing list
[hidden email]
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Reply | Threaded
Open this post in threaded view
|

Re: is there an easy way to do this?

cacb
On 2017-05-29 17:01, jon wrote:

> Imagine a sphere on which a shape has been drawn.  Let's say it is a
> circle.  Now, project that back to the center of the sphere, and you
> have a cone (of sorts: the base is on the surface of the sphere, and
> thus is not flat).
>
> If the original shape was a square, then the projected shape is a cube
> of sorts, one face of which has become a single point at the center of
> the sphere.
>
> Is there a simple way to specify the 2D shape and then create the 3D
> object?
>
> I do not actually want the object: I intend to use the object to cut
> out that cross section from a ring (torus).  The whole point is that
> the edges of the cutout all point in to the center of the ring/sphere.

If all you want is to cut the torus all the way out, just subtract a
tall enough pyramid with square base (polyhedron) or cone (cylinder with
r2=0) from the torus. Place the apex of the pyramid/cone at the center
of the torus.

Carsten Arnholm


_______________________________________________
OpenSCAD mailing list
[hidden email]
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Reply | Threaded
Open this post in threaded view
|

Re: is there an easy way to do this?

Ronaldo
jon, polar coordinates are the natural way to specify a 2D shape on the surface of a sphere. Then you can project the shape on a plane to get a shape to be linear_extruded (with scale=0) in a cone.

_______________________________________________
OpenSCAD mailing list
[hidden email]
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org