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teach me about polygons?

GH
Gene Heskett
Mon, Sep 6, 2021 11:40 PM

Greetings all;

I see a very simplified definition of polyhedron in the cheat sheet but
I'm not getting the mental concept.

I need to define a box that isn't quite square.,so it looks like a job
for a polyhedron. I have made 6 measurements that with some duplicate
useage, could define the 8 corner points of a tapered 3d box, within
which I need to build a stuffer that will serve to locate an alternating
side to side and lengthwise limits to the movements allowed for the
contents of the box.

An example of such a definition that I could plug my measurements into
would be a great help. I get the points=, but not the shown paths in the
docs example as it seems to me that the paths should specify a starting
point and and ending point, where the example shows a single number.

FWIW, there is not a top or bottom to the box in this idea, that is done
by separate parts that already exist.

Thanks all and take care.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.

Greetings all; I see a very simplified definition of polyhedron in the cheat sheet but I'm not getting the mental concept. I need to define a box that isn't quite square.,so it looks like a job for a polyhedron. I have made 6 measurements that with some duplicate useage, could define the 8 corner points of a tapered 3d box, within which I need to build a stuffer that will serve to locate an alternating side to side and lengthwise limits to the movements allowed for the contents of the box. An example of such a definition that I could plug my measurements into would be a great help. I get the points=, but not the shown paths in the docs example as it seems to me that the paths should specify a starting point and and ending point, where the example shows a single number. FWIW, there is not a top or bottom to the box in this idea, that is done by separate parts that already exist. Thanks all and take care. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
FH
Father Horton
Tue, Sep 7, 2021 12:46 AM

This is the example from the docs:

CubePoints = [
[  0,  0,  0 ],  //0
[ 10,  0,  0 ],  //1
[ 10,  7,  0 ],  //2
[  0,  7,  0 ],  //3
[  0,  0,  5 ],  //4
[ 10,  0,  5 ],  //5
[ 10,  7,  5 ],  //6
[  0,  7,  5 ]]; //7

CubeFaces = [
[0,1,2,3],  // bottom
[4,5,1,0],  // front
[7,6,5,4],  // top
[5,6,2,1],  // right
[6,7,3,2],  // back
[7,4,0,3]]; // left

The points are the 8 corner points you've already determined; what you have
to do now is to tell OpenSCAD how those go together to make faces. So the
bottom face is made up of points 0, 1, 2 and 3 (it closes the loop
implicitly), the top is 7, 6, 5 and 4, and so on. The tricky thing is that
you have to maintain a consistent direction as you specify the points that
make up a face. You have to go consistently either clockwise or
counterclockwise (from the outside looking in). You can't go back and
forth. That's why the points in CubeFaces are ordered the way they are.

On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett gheskett@shentel.net wrote:

Greetings all;

I see a very simplified definition of polyhedron in the cheat sheet but
I'm not getting the mental concept.

I need to define a box that isn't quite square.,so it looks like a job
for a polyhedron. I have made 6 measurements that with some duplicate
useage, could define the 8 corner points of a tapered 3d box, within
which I need to build a stuffer that will serve to locate an alternating
side to side and lengthwise limits to the movements allowed for the
contents of the box.

An example of such a definition that I could plug my measurements into
would be a great help. I get the points=, but not the shown paths in the
docs example as it seems to me that the paths should specify a starting
point and and ending point, where the example shows a single number.

FWIW, there is not a top or bottom to the box in this idea, that is done
by separate parts that already exist.

Thanks all and take care.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.


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

This is the example from the docs: CubePoints = [ [ 0, 0, 0 ], //0 [ 10, 0, 0 ], //1 [ 10, 7, 0 ], //2 [ 0, 7, 0 ], //3 [ 0, 0, 5 ], //4 [ 10, 0, 5 ], //5 [ 10, 7, 5 ], //6 [ 0, 7, 5 ]]; //7 CubeFaces = [ [0,1,2,3], // bottom [4,5,1,0], // front [7,6,5,4], // top [5,6,2,1], // right [6,7,3,2], // back [7,4,0,3]]; // left The points are the 8 corner points you've already determined; what you have to do now is to tell OpenSCAD how those go together to make faces. So the bottom face is made up of points 0, 1, 2 and 3 (it closes the loop implicitly), the top is 7, 6, 5 and 4, and so on. The tricky thing is that you have to maintain a consistent direction as you specify the points that make up a face. You have to go consistently either clockwise or counterclockwise (from the outside looking in). You can't go back and forth. That's why the points in CubeFaces are ordered the way they are. On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett <gheskett@shentel.net> wrote: > Greetings all; > > I see a very simplified definition of polyhedron in the cheat sheet but > I'm not getting the mental concept. > > I need to define a box that isn't quite square.,so it looks like a job > for a polyhedron. I have made 6 measurements that with some duplicate > useage, could define the 8 corner points of a tapered 3d box, within > which I need to build a stuffer that will serve to locate an alternating > side to side and lengthwise limits to the movements allowed for the > contents of the box. > > An example of such a definition that I could plug my measurements into > would be a great help. I get the points=, but not the shown paths in the > docs example as it seems to me that the paths should specify a starting > point and and ending point, where the example shows a single number. > > FWIW, there is not a top or bottom to the box in this idea, that is done > by separate parts that already exist. > > Thanks all and take care. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
FH
Father Horton
Tue, Sep 7, 2021 12:53 AM

By the way, if you just drop your measured points into CubePoints, it will
probably work.

On Mon, Sep 6, 2021 at 7:46 PM Father Horton fatherhorton@gmail.com wrote:

This is the example from the docs:

CubePoints = [
[  0,  0,  0 ],  //0
[ 10,  0,  0 ],  //1
[ 10,  7,  0 ],  //2
[  0,  7,  0 ],  //3
[  0,  0,  5 ],  //4
[ 10,  0,  5 ],  //5
[ 10,  7,  5 ],  //6
[  0,  7,  5 ]]; //7

CubeFaces = [
[0,1,2,3],  // bottom
[4,5,1,0],  // front
[7,6,5,4],  // top
[5,6,2,1],  // right
[6,7,3,2],  // back
[7,4,0,3]]; // left

The points are the 8 corner points you've already determined; what you
have to do now is to tell OpenSCAD how those go together to make faces. So
the bottom face is made up of points 0, 1, 2 and 3 (it closes the loop
implicitly), the top is 7, 6, 5 and 4, and so on. The tricky thing is that
you have to maintain a consistent direction as you specify the points that
make up a face. You have to go consistently either clockwise or
counterclockwise (from the outside looking in). You can't go back and
forth. That's why the points in CubeFaces are ordered the way they are.

On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett gheskett@shentel.net wrote:

Greetings all;

I see a very simplified definition of polyhedron in the cheat sheet but
I'm not getting the mental concept.

I need to define a box that isn't quite square.,so it looks like a job
for a polyhedron. I have made 6 measurements that with some duplicate
useage, could define the 8 corner points of a tapered 3d box, within
which I need to build a stuffer that will serve to locate an alternating
side to side and lengthwise limits to the movements allowed for the
contents of the box.

An example of such a definition that I could plug my measurements into
would be a great help. I get the points=, but not the shown paths in the
docs example as it seems to me that the paths should specify a starting
point and and ending point, where the example shows a single number.

FWIW, there is not a top or bottom to the box in this idea, that is done
by separate parts that already exist.

Thanks all and take care.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.


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

By the way, if you just drop your measured points into CubePoints, it will probably work. On Mon, Sep 6, 2021 at 7:46 PM Father Horton <fatherhorton@gmail.com> wrote: > This is the example from the docs: > > CubePoints = [ > [ 0, 0, 0 ], //0 > [ 10, 0, 0 ], //1 > [ 10, 7, 0 ], //2 > [ 0, 7, 0 ], //3 > [ 0, 0, 5 ], //4 > [ 10, 0, 5 ], //5 > [ 10, 7, 5 ], //6 > [ 0, 7, 5 ]]; //7 > > CubeFaces = [ > [0,1,2,3], // bottom > [4,5,1,0], // front > [7,6,5,4], // top > [5,6,2,1], // right > [6,7,3,2], // back > [7,4,0,3]]; // left > > The points are the 8 corner points you've already determined; what you > have to do now is to tell OpenSCAD how those go together to make faces. So > the bottom face is made up of points 0, 1, 2 and 3 (it closes the loop > implicitly), the top is 7, 6, 5 and 4, and so on. The tricky thing is that > you have to maintain a consistent direction as you specify the points that > make up a face. You have to go consistently either clockwise or > counterclockwise (from the outside looking in). You can't go back and > forth. That's why the points in CubeFaces are ordered the way they are. > > On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett <gheskett@shentel.net> wrote: > >> Greetings all; >> >> I see a very simplified definition of polyhedron in the cheat sheet but >> I'm not getting the mental concept. >> >> I need to define a box that isn't quite square.,so it looks like a job >> for a polyhedron. I have made 6 measurements that with some duplicate >> useage, could define the 8 corner points of a tapered 3d box, within >> which I need to build a stuffer that will serve to locate an alternating >> side to side and lengthwise limits to the movements allowed for the >> contents of the box. >> >> An example of such a definition that I could plug my measurements into >> would be a great help. I get the points=, but not the shown paths in the >> docs example as it seems to me that the paths should specify a starting >> point and and ending point, where the example shows a single number. >> >> FWIW, there is not a top or bottom to the box in this idea, that is done >> by separate parts that already exist. >> >> Thanks all and take care. >> >> Cheers, Gene Heskett >> -- >> "There are four boxes to be used in defense of liberty: >> soap, ballot, jury, and ammo. Please use in that order." >> -Ed Howdershelt (Author) >> If we desire respect for the law, we must first make the law respectable. >> - Louis D. Brandeis >> Genes Web page <http://geneslinuxbox.net:6309/gene> >> _______________________________________________ >> OpenSCAD mailing list >> To unsubscribe send an email to discuss-leave@lists.openscad.org >> >
GH
Gene Heskett
Tue, Sep 7, 2021 2:25 AM

On Monday 06 September 2021 20:46:16 Father Horton wrote:

This is the example from the docs:

CubePoints = [
[  0,  0,  0 ],  //0
[ 10,  0,  0 ],  //1
[ 10,  7,  0 ],  //2
[  0,  7,  0 ],  //3
[  0,  0,  5 ],  //4
[ 10,  0,  5 ],  //5
[ 10,  7,  5 ],  //6
[  0,  7,  5 ]]; //7

CubeFaces = [
[0,1,2,3],  // bottom
[4,5,1,0],  // front
[7,6,5,4],  // top
[5,6,2,1],  // right
[6,7,3,2],  // back
[7,4,0,3]]; // left

The points are the 8 corner points you've already determined; what you
have to do now is to tell OpenSCAD how those go together to make
faces. So the bottom face is made up of points 0, 1, 2 and 3 (it
closes the loop implicitly), the top is 7, 6, 5 and 4, and so on. The
tricky thing is that you have to maintain a consistent direction as
you specify the points that make up a face. You have to go
consistently either clockwise or counterclockwise (from the outside
looking in). You can't go back and forth. That's why the points in
CubeFaces are ordered the way they are.

It finally sank in that the cw/ccw is per face, not around the box. so
now I get that. But I don't need a top or bottom.  So how do I reorder
to leave out the top and bottom, all I want are the sides which will
then be built up on the inside to do the job, effectively winding up on
the printer as a half box with a big difference removing about half the
box. These measurements only serve to define the outside dimensions of
the part I'm actually building. And it needs a 30 degree angle on the
edges of the ends cut off. That can be done later so its not an instant
problem ATM.

I'll see if some sleep helps.

Thank you.

On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett gheskett@shentel.net

wrote:

Greetings all;

I see a very simplified definition of polyhedron in the cheat sheet
but I'm not getting the mental concept.

I need to define a box that isn't quite square.,so it looks like a
job for a polyhedron. I have made 6 measurements that with some
duplicate useage, could define the 8 corner points of a tapered 3d
box, within which I need to build a stuffer that will serve to
locate an alternating side to side and lengthwise limits to the
movements allowed for the contents of the box.

An example of such a definition that I could plug my measurements
into would be a great help. I get the points=, but not the shown
paths in the docs example as it seems to me that the paths should
specify a starting point and and ending point, where the example
shows a single number.

FWIW, there is not a top or bottom to the box in this idea, that is
done by separate parts that already exist.

Thanks all and take care.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.

On Monday 06 September 2021 20:46:16 Father Horton wrote: > This is the example from the docs: > > CubePoints = [ > [ 0, 0, 0 ], //0 > [ 10, 0, 0 ], //1 > [ 10, 7, 0 ], //2 > [ 0, 7, 0 ], //3 > [ 0, 0, 5 ], //4 > [ 10, 0, 5 ], //5 > [ 10, 7, 5 ], //6 > [ 0, 7, 5 ]]; //7 > > CubeFaces = [ > [0,1,2,3], // bottom > [4,5,1,0], // front > [7,6,5,4], // top > [5,6,2,1], // right > [6,7,3,2], // back > [7,4,0,3]]; // left > > The points are the 8 corner points you've already determined; what you > have to do now is to tell OpenSCAD how those go together to make > faces. So the bottom face is made up of points 0, 1, 2 and 3 (it > closes the loop implicitly), the top is 7, 6, 5 and 4, and so on. The > tricky thing is that you have to maintain a consistent direction as > you specify the points that make up a face. You have to go > consistently either clockwise or counterclockwise (from the outside > looking in). You can't go back and forth. That's why the points in > CubeFaces are ordered the way they are. > It finally sank in that the cw/ccw is per face, not around the box. so now I get that. But I don't need a top or bottom. So how do I reorder to leave out the top and bottom, all I want are the sides which will then be built up on the inside to do the job, effectively winding up on the printer as a half box with a big difference removing about half the box. These measurements only serve to define the outside dimensions of the part I'm actually building. And it needs a 30 degree angle on the edges of the ends cut off. That can be done later so its not an instant problem ATM. I'll see if some sleep helps. Thank you. > On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett <gheskett@shentel.net> wrote: > > Greetings all; > > > > I see a very simplified definition of polyhedron in the cheat sheet > > but I'm not getting the mental concept. > > > > I need to define a box that isn't quite square.,so it looks like a > > job for a polyhedron. I have made 6 measurements that with some > > duplicate useage, could define the 8 corner points of a tapered 3d > > box, within which I need to build a stuffer that will serve to > > locate an alternating side to side and lengthwise limits to the > > movements allowed for the contents of the box. > > > > An example of such a definition that I could plug my measurements > > into would be a great help. I get the points=, but not the shown > > paths in the docs example as it seems to me that the paths should > > specify a starting point and and ending point, where the example > > shows a single number. > > > > FWIW, there is not a top or bottom to the box in this idea, that is > > done by separate parts that already exist. > > > > Thanks all and take care. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
GH
Gene Heskett
Tue, Sep 7, 2021 2:31 AM

On Monday 06 September 2021 20:53:53 Father Horton wrote:

By the way, if you just drop your measured points into CubePoints, it
will probably work.

I tried to outsmart myself by doing a /2 on the xy stuff so it would be
self centering on the build plate by using value, -value in the arrays.
I think that may be contributing to my confusion.

Thanks Father Horton.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.

On Monday 06 September 2021 20:53:53 Father Horton wrote: > By the way, if you just drop your measured points into CubePoints, it > will probably work. > I tried to outsmart myself by doing a /2 on the xy stuff so it would be self centering on the build plate by using value, -value in the arrays. I think that may be contributing to my confusion. Thanks Father Horton. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
M
MichaelAtOz
Tue, Sep 7, 2021 6:19 AM

A picture is worth a thousand words.

Sounds like you want outside thickness.

Similar to this triangular example (lower corrected one) from:

https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#Mis-ordered_faces

polyhedron

(points = [

        [0, -10, 60], [0, 10, 60], [0, 10, 0], [0, -10, 0], [60, -10, 60], [60, 10, 60], 

        [10, -10, 50], [10, 10, 50], [10, 10, 30], [10, -10, 30], [30, -10, 50], [30, 10, 50]

        ], 

 faces = [

         [0,3,2],  [0,2,1],  [4,0,5],  [5,0,1],  [5,2,4],  [4,2,3],

              [6,8,9],  [6,7,8],  [6,10,11],[6,11,7], [10,8,11],

         [10,9,8], [3,0,9],  [9,0,6],  [10,6, 0],[0,4,10],

              [3,9,10], [3,10,4], [1,7,11], [1,11,5], [1,8,7],  

              [2,8,1],  [8,2,11], [5,11,2]

         ]

 );

-----Original Message-----

From: Gene Heskett [mailto:gheskett@shentel.net]

Sent: Tue, 7 Sep 2021 12:31

Subject: [OpenSCAD] Re: teach me about polygons?

On Monday 06 September 2021 20:53:53 Father Horton wrote:

By the way, if you just drop your measured points into CubePoints, it

will probably work.

I tried to outsmart myself by doing a /2 on the xy stuff so it would be

self centering on the build plate by using value, -value in the arrays.

I think that may be contributing to my confusion.

Thanks Father Horton.

Cheers, Gene Heskett

--

"There are four boxes to be used in defense of liberty:

soap, ballot, jury, and ammo. Please use in that order."

-Ed Howdershelt (Author)

If we desire respect for the law, we must first make the law respectable.

  • Louis D. Brandeis

OpenSCAD mailing list

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

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

A picture is worth a thousand words. Sounds like you want outside thickness. Similar to this triangular example (lower corrected one) from: https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#Mis-ordered_faces polyhedron (points = [ [0, -10, 60], [0, 10, 60], [0, 10, 0], [0, -10, 0], [60, -10, 60], [60, 10, 60], [10, -10, 50], [10, 10, 50], [10, 10, 30], [10, -10, 30], [30, -10, 50], [30, 10, 50] ], faces = [ [0,3,2], [0,2,1], [4,0,5], [5,0,1], [5,2,4], [4,2,3], [6,8,9], [6,7,8], [6,10,11],[6,11,7], [10,8,11], [10,9,8], [3,0,9], [9,0,6], [10,6, 0],[0,4,10], [3,9,10], [3,10,4], [1,7,11], [1,11,5], [1,8,7], [2,8,1], [8,2,11], [5,11,2] ] ); > -----Original Message----- > From: Gene Heskett [mailto:gheskett@shentel.net] > Sent: Tue, 7 Sep 2021 12:31 > To: discuss@lists.openscad.org > Subject: [OpenSCAD] Re: teach me about polygons? > > On Monday 06 September 2021 20:53:53 Father Horton wrote: > > > By the way, if you just drop your measured points into CubePoints, it > > will probably work. > > > I tried to outsmart myself by doing a /2 on the xy stuff so it would be > self centering on the build plate by using value, -value in the arrays. > I think that may be contributing to my confusion. > > Thanks Father Horton. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org -- This email has been checked for viruses by AVG. https://www.avg.com
RP
Ronaldo Persiano
Tue, Sep 7, 2021 7:54 AM

It is not clear to me why you need a polyhedron with missing faces but to
get it just drop the faces you don't want from the list of faces of
the polyhedron. However, it should be clear that the incomplete polyhedron,
which doesn't enclose a volume, will not be rendered (F6) and so no STL is
possible to be produced although OpenSCAD is able to produce the expected
image in a preview (F5).

Note also that a cube without the top face unioned with a similar cube
positioned on top of it but without its bottom face will not be assembled
as a valid object. Each polyhedron in a boolean operation (union,
intersection or difference) should be valid by itself, that is, enclose a
volume.

For each polyhedron you define, check it with View/Thrown Together. Faces
with inconsistent windings will be shown with different colors.

Em ter., 7 de set. de 2021 às 03:25, Gene Heskett gheskett@shentel.net
escreveu:

On Monday 06 September 2021 20:46:16 Father Horton wrote:

This is the example from the docs:

CubePoints = [
[  0,  0,  0 ],  //0
[ 10,  0,  0 ],  //1
[ 10,  7,  0 ],  //2
[  0,  7,  0 ],  //3
[  0,  0,  5 ],  //4
[ 10,  0,  5 ],  //5
[ 10,  7,  5 ],  //6
[  0,  7,  5 ]]; //7

CubeFaces = [
[0,1,2,3],  // bottom
[4,5,1,0],  // front
[7,6,5,4],  // top
[5,6,2,1],  // right
[6,7,3,2],  // back
[7,4,0,3]]; // left

The points are the 8 corner points you've already determined; what you
have to do now is to tell OpenSCAD how those go together to make
faces. So the bottom face is made up of points 0, 1, 2 and 3 (it
closes the loop implicitly), the top is 7, 6, 5 and 4, and so on. The
tricky thing is that you have to maintain a consistent direction as
you specify the points that make up a face. You have to go
consistently either clockwise or counterclockwise (from the outside
looking in). You can't go back and forth. That's why the points in
CubeFaces are ordered the way they are.

It finally sank in that the cw/ccw is per face, not around the box. so
now I get that. But I don't need a top or bottom.  So how do I reorder
to leave out the top and bottom, all I want are the sides which will
then be built up on the inside to do the job, effectively winding up on
the printer as a half box with a big difference removing about half the
box. These measurements only serve to define the outside dimensions of
the part I'm actually building. And it needs a 30 degree angle on the
edges of the ends cut off. That can be done later so its not an instant
problem ATM.

I'll see if some sleep helps.

Thank you.

On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett gheskett@shentel.net

wrote:

Greetings all;

I see a very simplified definition of polyhedron in the cheat sheet
but I'm not getting the mental concept.

I need to define a box that isn't quite square.,so it looks like a
job for a polyhedron. I have made 6 measurements that with some
duplicate useage, could define the 8 corner points of a tapered 3d
box, within which I need to build a stuffer that will serve to
locate an alternating side to side and lengthwise limits to the
movements allowed for the contents of the box.

An example of such a definition that I could plug my measurements
into would be a great help. I get the points=, but not the shown
paths in the docs example as it seems to me that the paths should
specify a starting point and and ending point, where the example
shows a single number.

FWIW, there is not a top or bottom to the box in this idea, that is
done by separate parts that already exist.

Thanks all and take care.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.


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It is not clear to me why you need a polyhedron with missing faces but to get it just drop the faces you don't want from the list of faces of the polyhedron. However, it should be clear that the incomplete polyhedron, which doesn't enclose a volume, will not be rendered (F6) and so no STL is possible to be produced although OpenSCAD is able to produce the expected image in a preview (F5). Note also that a cube without the top face unioned with a similar cube positioned on top of it but without its bottom face will not be assembled as a valid object. Each polyhedron in a boolean operation (union, intersection or difference) should be valid by itself, that is, enclose a volume. For each polyhedron you define, check it with View/Thrown Together. Faces with inconsistent windings will be shown with different colors. Em ter., 7 de set. de 2021 às 03:25, Gene Heskett <gheskett@shentel.net> escreveu: > On Monday 06 September 2021 20:46:16 Father Horton wrote: > > > This is the example from the docs: > > > > CubePoints = [ > > [ 0, 0, 0 ], //0 > > [ 10, 0, 0 ], //1 > > [ 10, 7, 0 ], //2 > > [ 0, 7, 0 ], //3 > > [ 0, 0, 5 ], //4 > > [ 10, 0, 5 ], //5 > > [ 10, 7, 5 ], //6 > > [ 0, 7, 5 ]]; //7 > > > > CubeFaces = [ > > [0,1,2,3], // bottom > > [4,5,1,0], // front > > [7,6,5,4], // top > > [5,6,2,1], // right > > [6,7,3,2], // back > > [7,4,0,3]]; // left > > > > The points are the 8 corner points you've already determined; what you > > have to do now is to tell OpenSCAD how those go together to make > > faces. So the bottom face is made up of points 0, 1, 2 and 3 (it > > closes the loop implicitly), the top is 7, 6, 5 and 4, and so on. The > > tricky thing is that you have to maintain a consistent direction as > > you specify the points that make up a face. You have to go > > consistently either clockwise or counterclockwise (from the outside > > looking in). You can't go back and forth. That's why the points in > > CubeFaces are ordered the way they are. > > > It finally sank in that the cw/ccw is per face, not around the box. so > now I get that. But I don't need a top or bottom. So how do I reorder > to leave out the top and bottom, all I want are the sides which will > then be built up on the inside to do the job, effectively winding up on > the printer as a half box with a big difference removing about half the > box. These measurements only serve to define the outside dimensions of > the part I'm actually building. And it needs a 30 degree angle on the > edges of the ends cut off. That can be done later so its not an instant > problem ATM. > > I'll see if some sleep helps. > > Thank you. > > > On Mon, Sep 6, 2021 at 6:41 PM Gene Heskett <gheskett@shentel.net> > wrote: > > > Greetings all; > > > > > > I see a very simplified definition of polyhedron in the cheat sheet > > > but I'm not getting the mental concept. > > > > > > I need to define a box that isn't quite square.,so it looks like a > > > job for a polyhedron. I have made 6 measurements that with some > > > duplicate useage, could define the 8 corner points of a tapered 3d > > > box, within which I need to build a stuffer that will serve to > > > locate an alternating side to side and lengthwise limits to the > > > movements allowed for the contents of the box. > > > > > > An example of such a definition that I could plug my measurements > > > into would be a great help. I get the points=, but not the shown > > > paths in the docs example as it seems to me that the paths should > > > specify a starting point and and ending point, where the example > > > shows a single number. > > > > > > FWIW, there is not a top or bottom to the box in this idea, that is > > > done by separate parts that already exist. > > > > > > Thanks all and take care. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
GH
Gene Heskett
Tue, Sep 7, 2021 11:31 AM

On Monday 06 September 2021 22:31:22 Gene Heskett wrote:

On Monday 06 September 2021 20:53:53 Father Horton wrote:

By the way, if you just drop your measured points into CubePoints,
it will probably work.

I tried to outsmart myself by doing a /2 on the xy stuff so it would
be self centering on the build plate by using value, -value in the
arrays. I think that may be contributing to my confusion.

Thanks Father Horton.

Cheers, Gene Heskett

OK, I got that box, all yellow so I assume its right. But its now a solid
box. How do I remove the top and bottom faces so I can work inside
this "bounding box"

Got that too, but the inside is all magenta. Is that fixable or
ignorable? In any event I now have the "bounding box"

I then made a union between 2 polyhedrons, one inside the other, but it
didn't fill the gap between them, how is that done?

And when I meant to simplicate it by doing addition and subtraction
between 2 valid vars in the list of points, I got told I cannot do that.

Do I have to predefine every var I use in a point list in a separate
varname=value; or varname=[var1-var2]/2; statement?  This will quickly
take the define statements to different places in the file requiring
huge amounts of scrolling back and forth to keep track of the point and
face lists.

I note the docs do not show vars, just integer numbers. But they appear
to work as long as they are predefned first.

Progress, slowly as the rules begin to become more obvious as I stumble
over the violations.

Thank you.

Cheers, Gene Heskett

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.

On Monday 06 September 2021 22:31:22 Gene Heskett wrote: > On Monday 06 September 2021 20:53:53 Father Horton wrote: > > By the way, if you just drop your measured points into CubePoints, > > it will probably work. > > I tried to outsmart myself by doing a /2 on the xy stuff so it would > be self centering on the build plate by using value, -value in the > arrays. I think that may be contributing to my confusion. > > Thanks Father Horton. > > Cheers, Gene Heskett OK, I got that box, all yellow so I assume its right. But its now a solid box. How do I remove the top and bottom faces so I can work inside this "bounding box" Got that too, but the inside is all magenta. Is that fixable or ignorable? In any event I now have the "bounding box" I then made a union between 2 polyhedrons, one inside the other, but it didn't fill the gap between them, how is that done? And when I meant to simplicate it by doing addition and subtraction between 2 valid vars in the list of points, I got told I cannot do that. Do I have to predefine every var I use in a point list in a separate varname=value; or varname=[var1-var2]/2; statement? This will quickly take the define statements to different places in the file requiring huge amounts of scrolling back and forth to keep track of the point and face lists. I note the docs do not show vars, just integer numbers. But they appear to work as long as they are predefned first. Progress, slowly as the rules begin to become more obvious as I stumble over the violations. Thank you. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
RW
Ray West
Tue, Sep 7, 2021 11:34 AM

On 07/09/2021 08:54, Ronaldo Persiano wrote:

So how do I reorder
to leave out the top and bottom, all I want are the sides which will
then be built up on the inside to do the job, effectively winding up on
the printer as a half box with a big difference removing about half the
box.

I'm still not sure what it looks like to you, but to me, from the above
description, it would be two polygons (not polyhedron) , one inside the
other, extruded, and top and bottom chopped off however you want by
differences.  That will give a solid, and you can add features/whatever,
as you wish.

On 07/09/2021 08:54, Ronaldo Persiano wrote: > So how do I reorder > to leave out the top and bottom, all I want are the sides which will > then be built up on the inside to do the job, effectively winding up on > the printer as a half box with a big difference removing about half the > box. I'm still not sure what it looks like to you, but to me, from the above description, it would be two polygons (not polyhedron) , one inside the other, extruded, and top and bottom chopped off however you want by differences.  That will give a solid, and you can add features/whatever, as you wish.
NH
nop head
Tue, Sep 7, 2021 12:07 PM

You can't take a face of the polyhedron to get an open box. It is not a
manifold solid because the walls would infinitely thin. If it is an
irregular shape that can't be linear_extruded then make two solid
polyhedra, one for the outside and one for the inside and subtract them.

You don't need variables for each point in the polyhedra, they can be any
expression.

On Tue, 7 Sept 2021 at 12:35, Ray West raywest@raywest.com wrote:

On 07/09/2021 08:54, Ronaldo Persiano wrote:

So how do I reorder
to leave out the top and bottom, all I want are the sides which will
then be built up on the inside to do the job, effectively winding up on
the printer as a half box with a big difference removing about half the
box.

I'm still not sure what it looks like to you, but to me, from the above
description, it would be two polygons (not polyhedron) , one inside the
other, extruded, and top and bottom chopped off however you want by
differences.  That will give a solid, and you can add features/whatever,
as you wish.


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

You can't take a face of the polyhedron to get an open box. It is not a manifold solid because the walls would infinitely thin. If it is an irregular shape that can't be linear_extruded then make two solid polyhedra, one for the outside and one for the inside and subtract them. You don't need variables for each point in the polyhedra, they can be any expression. On Tue, 7 Sept 2021 at 12:35, Ray West <raywest@raywest.com> wrote: > > On 07/09/2021 08:54, Ronaldo Persiano wrote: > > So how do I reorder > > to leave out the top and bottom, all I want are the sides which will > > then be built up on the inside to do the job, effectively winding up on > > the printer as a half box with a big difference removing about half the > > box. > > > I'm still not sure what it looks like to you, but to me, from the above > description, it would be two polygons (not polyhedron) , one inside the > other, extruded, and top and bottom chopped off however you want by > differences. That will give a solid, and you can add features/whatever, > as you wish. > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >