Newbie rotation confusion.

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

Newbie rotation confusion.

Aurum
Having now subscribed to the mailing list hopefully this will now be posted.
Sorry if it's posted twice.

What I'm trying to do is understand how to get a cube at the origin with
it's corners on the axes.

Firstly, I tried rotating by 45° about x and y with no success.

I then rotated 45° about the X axis with
rotate(45,[1,0,0]){
    color("cyan") cube(10,center=true);
}
and looked down the Y axis. What I see is this.
<http://forum.openscad.org/file/t2335/cube1.png>

I now realize that I'm not looking at a square anymore but a rectangle with
sides 10 and 14.14 (10 x root 2) and so to align the corners with the Z axis
I need to rotate by atan(1.414) = 54.7°.

I do this with
rotate(45,[1,0,0]){
    rotate(54.7,[0,1,0]){
        color("cyan") cube(10,center=true);
    }
}
and the result is
<http://forum.openscad.org/file/t2335/cube2.png>

What am I doing wrong?

Is there a simple way to get a cube at the origin with it's corners on the
axes?

Mike.



--
Sent from: http://forum.openscad.org/

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

Re: Newbie rotation confusion.

nophead
>Is there a simple way to get a cube at the origin with it's corners on the axes?

No it is physically impossible.

On 7 September 2018 at 10:06, Aurum <[hidden email]> wrote:
Having now subscribed to the mailing list hopefully this will now be posted.
Sorry if it's posted twice.

What I'm trying to do is understand how to get a cube at the origin with
it's corners on the axes.

Firstly, I tried rotating by 45° about x and y with no success.

I then rotated 45° about the X axis with
rotate(45,[1,0,0]){
    color("cyan") cube(10,center=true);
}
and looked down the Y axis. What I see is this.
<http://forum.openscad.org/file/t2335/cube1.png>

I now realize that I'm not looking at a square anymore but a rectangle with
sides 10 and 14.14 (10 x root 2) and so to align the corners with the Z axis
I need to rotate by atan(1.414) = 54.7°.

I do this with
rotate(45,[1,0,0]){
    rotate(54.7,[0,1,0]){
        color("cyan") cube(10,center=true);
    }
}
and the result is
<http://forum.openscad.org/file/t2335/cube2.png>

What am I doing wrong?

Is there a simple way to get a cube at the origin with it's corners on the
axes?

Mike.



--
Sent from: http://forum.openscad.org/

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


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

Re: Newbie rotation confusion.

rew
On Fri, Sep 07, 2018 at 10:47:15AM +0100, nop head wrote:
> >Is there a simple way to get a cube at the origin with it's corners on the
> axes?
>
> No it is physically impossible.

Technically correct, but

rotate ([0,atan (sqrt(2)),0])
  rotate ([0,0,45])
    cube (40, center=true);

is what he was asking for.... I think.

Roger.


>
> On 7 September 2018 at 10:06, Aurum <[hidden email]> wrote:
>
> > Having now subscribed to the mailing list hopefully this will now be
> > posted.
> > Sorry if it's posted twice.
> >
> > What I'm trying to do is understand how to get a cube at the origin with
> > it's corners on the axes.
> >
> > Firstly, I tried rotating by 45° about x and y with no success.
> >
> > I then rotated 45° about the X axis with
> > rotate(45,[1,0,0]){
> >     color("cyan") cube(10,center=true);
> > }
> > and looked down the Y axis. What I see is this.
> > <http://forum.openscad.org/file/t2335/cube1.png>
> >
> > I now realize that I'm not looking at a square anymore but a rectangle with
> > sides 10 and 14.14 (10 x root 2) and so to align the corners with the Z
> > axis
> > I need to rotate by atan(1.414) = 54.7°.
> >
> > I do this with
> > rotate(45,[1,0,0]){
> >     rotate(54.7,[0,1,0]){
> >         color("cyan") cube(10,center=true);
> >     }
> > }
> > and the result is
> > <http://forum.openscad.org/file/t2335/cube2.png>
> >
> > What am I doing wrong?
> >
> > Is there a simple way to get a cube at the origin with it's corners on the
> > axes?
> >
> > Mike.
> >
> >
> >
> > --
> > Sent from: http://forum.openscad.org/
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > [hidden email]
> > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
> >

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


--
** [hidden email] ** http://www.BitWizard.nl/ ** +31-15-2600998 **
**    Delftechpark 26 2628 XH  Delft, The Netherlands. KVK: 27239233    **
*-- BitWizard writes Linux device drivers for any device you may have! --*
The plan was simple, like my brother-in-law Phil. But unlike
Phil, this plan just might work.

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

Re: Newbie rotation confusion.

nophead
A cube has 8 corners but there are only 6 points if one is on each half axis.

An object with all corners on an axis has triangular faces and looks like this:




On 7 September 2018 at 11:26, Rogier Wolff <[hidden email]> wrote:
On Fri, Sep 07, 2018 at 10:47:15AM +0100, nop head wrote:
> >Is there a simple way to get a cube at the origin with it's corners on the
> axes?
>
> No it is physically impossible.

Technically correct, but

rotate ([0,atan (sqrt(2)),0])
  rotate ([0,0,45])
    cube (40, center=true);

is what he was asking for.... I think.

Roger.


>
> On 7 September 2018 at 10:06, Aurum <[hidden email]> wrote:
>
> > Having now subscribed to the mailing list hopefully this will now be
> > posted.
> > Sorry if it's posted twice.
> >
> > What I'm trying to do is understand how to get a cube at the origin with
> > it's corners on the axes.
> >
> > Firstly, I tried rotating by 45° about x and y with no success.
> >
> > I then rotated 45° about the X axis with
> > rotate(45,[1,0,0]){
> >     color("cyan") cube(10,center=true);
> > }
> > and looked down the Y axis. What I see is this.
> > <http://forum.openscad.org/file/t2335/cube1.png>
> >
> > I now realize that I'm not looking at a square anymore but a rectangle with
> > sides 10 and 14.14 (10 x root 2) and so to align the corners with the Z
> > axis
> > I need to rotate by atan(1.414) = 54.7°.
> >
> > I do this with
> > rotate(45,[1,0,0]){
> >     rotate(54.7,[0,1,0]){
> >         color("cyan") cube(10,center=true);
> >     }
> > }
> > and the result is
> > <http://forum.openscad.org/file/t2335/cube2.png>
> >
> > What am I doing wrong?
> >
> > Is there a simple way to get a cube at the origin with it's corners on the
> > axes?
> >
> > Mike.
> >
> >
> >
> > --
> > Sent from: http://forum.openscad.org/
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > [hidden email]
> > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
> >

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


--
** [hidden email] ** http://www.BitWizard.nl/ ** +31-15-2600998 **
**    Delftechpark 26 2628 XH  Delft, The Netherlands. KVK: 27239233    **
*-- BitWizard writes Linux device drivers for any device you may have! --*
The plan was simple, like my brother-in-law Phil. But unlike
Phil, this plan just might work.

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


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

Re: Newbie rotation confusion.

Aurum
Thank you, it makes sense now. I'm thinking of the axis coming out of each
face and (incorrectly) visualized them coming out of the corners. Actually,
that double pyramid shape will achieve the effect I'm after.
I'm assuming cube(10,10,0.001) gives the pyramid.

Time to play some more.

Thanks all,

Mike.



--
Sent from: http://forum.openscad.org/

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

Re: Newbie rotation confusion.

nophead
>I'm assuming cube(10,10,0.001) gives the pyramid.

It gives approximately a square. The hull of that and one rotated 90 degrees gives the pyramid.

Hull only works on 3D shapes unfortunately.

On 7 September 2018 at 11:57, Aurum <[hidden email]> wrote:
Thank you, it makes sense now. I'm thinking of the axis coming out of each
face and (incorrectly) visualized them coming out of the corners. Actually,
that double pyramid shape will achieve the effect I'm after.
I'm assuming cube(10,10,0.001) gives the pyramid.

Time to play some more.

Thanks all,

Mike.



--
Sent from: http://forum.openscad.org/

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


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

Re: Newbie rotation confusion.

NateTG
In reply to this post by Aurum
> ... I'm thinking of the axis coming out of each face and (incorrectly)
visualized them coming out of the corners. ...

You can do that with: 'cube([10,10,10],center=true)' or using a translation.





--
Sent from: http://forum.openscad.org/

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

Re: Newbie rotation confusion.

thehans
In reply to this post by Aurum
The double pyramid shape is also known as an octahedron and is one of
the Platonic solids.

Here's another way to make one using "cylinders".
for (k = [0,1]) mirror([0,0,k])
 cylinder(r1=1,r2=0,h=1, $fn=4);

Another alternative would be to construct one from points and faces
using the polyhedron module.
On Fri, Sep 7, 2018 at 5:58 AM Aurum <[hidden email]> wrote:

>
> Thank you, it makes sense now. I'm thinking of the axis coming out of each
> face and (incorrectly) visualized them coming out of the corners. Actually,
> that double pyramid shape will achieve the effect I'm after.
> I'm assuming cube(10,10,0.001) gives the pyramid.
>
> Time to play some more.
>
> Thanks all,
>
> Mike.
>
>
>
> --
> Sent from: http://forum.openscad.org/
>
> _______________________________________________
> OpenSCAD mailing list
> [hidden email]
> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

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