best way to create this
1) No you don't have one. If you did it would be easier to describe.
Two of them pushed together (one a mirror image) would make sort of an
egg holder.
2) No
3) Nothing
4) Dimensions don't matter, it will vary in size.
5) All areas are critical. Not sure how to answer this.
6) See image
This is sort of what I am aiming for. I was wondering if there is
another way to create it. I would like the inside to be concave instead
of a hard straight slope down. I put my ugly code below that.
$fn=100;
height=20;
base=30;
for (i=[0:1:180]){
rotate ([0,0,-i]){
translate ([-base-3+(i/10),0,0])
rotate ([270,0,0]){
linear_extrude(height = 1, center = false, convexity = 10,
twist = 0)
polygon (points=[[0,0],[0,-height+(i/15)],[base-(i/10),0]]);
}
}
}
Lee
On 2/25/2021 8:22 PM, Ron Wheeler via Discuss wrote:
People seem to have a very hard time to imagine what you actually want.
- Do I already have one of these in my home?
- Is it a replacement part?
- What does it have to mesh/interface with?
- What are the critical or known dimensions? What dimensions don't
really matter? - What are the critical areas in the shape? Distance between points
on your drawing or radius of curves, etc. - If you don't bend it over, what would it look like (dimensions and
important radia please)
I don't recall seeing anything like this in my house.
On 2021-02-25 6:19 p.m., Lee A wrote:
It is supposed to be 3D.
I would say the inverse of your image with the pointy tip on the inside.
Take a bowl and pull/stretch the bottom center to the right side a
bit. Then cut it in half vertically with the blade going left to
right. Trying to go from my mind to your mind without telepathy and
not coming up with the right words.
How did you do your example? Maybe I can just reverse that.
I would like to smooth it by using something better than triangles,
some shape I design with rounding.
Lee
On 2/25/2021 4:37 PM, adrianv wrote:
Your picture looked like a flat 2d picture of triangles and an arc.
So Is this sort of like what you're after?
Note: the triangles are coplanar but it doesn't look like it because
of the shrinkage along the length which means the small one is not
aligned with the big one.
Leea wrote
It is defined by the dimensions of the triangles.
I am trying to figure out how to explain it. Imagine a triangular
'rod'
that diminishes in size in all three dimensions from one end to the
other. Then bend that rod into a U shape. So it is a solid
piece. The
inner arc is small and could be a circle. The outer arc is almost
half a
circle but a bit elliptical. It could be circle if needed. Ideally
the
hypotenuse would be a little concave but I was going to live with
straight. I was hoping a picture was worth a lot of words.
Lee
On 2/25/2021 3:59 PM, adrianv wrote:
> I think you need to give more information about what you're
trying to
> create. Is the shape defined by the dimensions of the
triangles? The
> space between them? Or maybe by some dimensions and some
angles? And
> then an altitude? Are the arcs circles? They don't look like
it, so
> maybe not. What defines the arcs?
>
> I think knowing exactly what you're trying to create is an
important
> first step.
>
> Leea wrote
> I am sort of new and I manage to get along but probably not
in the
> best
> or most efficient way. I marvel at some of the code I see. I
want to
> create this and want to know the best way. All I come up
with is a
> series of thin triangles in a arc, each a different size.
How do I
> do it?
>
>
>
> thanks
> Lee
>
>
>
>
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Daniel was real close when he said amphitheater. I wish I had thought of
that word, it would have saved a lot.
Adrianv, Yep, you got it, nailed it. I hadn't heard of BOSL so I have to
research that. Thanks much. If I figure out BOSL I can make exactly what
I want from your start.
Lee
On 2/25/2021 8:44 PM, adrianv wrote:
In OpenSCAD ultimately everything is a triangle. (Maybe you can make
rectangles too?) There are no curves. So I'm not sure what you're
hoping for about "something better than triangles". Do you mean for
the end of the shape?
You said you want the hypotenuse a little concave? So here's a new
version. My code is based on the BOSL2 library. You might be able to
make a shape like this without a library by subtracting a sphere from
a cylinder. It would be more symmetric, though. The outer arc of th
shape produced by the code below is not a circle.
https://github.com/revarbat/BOSL2/wiki
https://github.com/revarbat/BOSL2/wiki
include <BOSL2/std.scad>
include <BOSL2/skin.scad>
include <BOSL2/turtle3d.scad>
include <BOSL2/rounding.scad>
$fn=128;
width = 10;
height = 8;
curve=2; // Amount to curve hypotenuse inward
normal = line_normal([[-height,width],[0,0]]);
//triangle = [[-height,width],[0,0],[0,width]]; // Straight side
triangle
triangle = [ each arc(points=[[-height,width],
[-height,width]/2+normal*curve, [0,0]]),
[0,0],
[0,width]
];
trans = turtle3d([
["arc", 4, "right", 180, "shrink", 2]
],transforms=true);
sweep(triangle, trans);
Leea wrote
It is supposed to be 3D.
I would say the inverse of your image with the pointy tip on the
inside.
Take a bowl and pull/stretch the bottom center to the right side a
bit.
Then cut it in half vertically with the blade going left to right.
Trying to go from my mind to your mind without telepathy and not
coming
up with the right words.
How did you do your example? Maybe I can just reverse that.
I would like to smooth it by using something better than
triangles, some
shape I design with rounding.
Lee
On 2/25/2021 4:37 PM, adrianv wrote:
Your picture looked like a flat 2d picture of triangles and an arc.
So Is this sort of like what you're after?
Note: the triangles are coplanar but it doesn't look like it
because
of the shrinkage along the length which means the small one is not
aligned with the big one.
Leea wrote
It is defined by the dimensions of the triangles.
I am trying to figure out how to explain it. Imagine a
triangular
'rod'
that diminishes in size in all three dimensions from one end
to the
other. Then bend that rod into a U shape. So it is a solid
piece. The
inner arc is small and could be a circle. The outer arc is
almost
half a
circle but a bit elliptical. It could be circle if needed.
Ideally
the
hypotenuse would be a little concave but I was going to live
with
straight. I was hoping a picture was worth a lot of words.
Lee
On 2/25/2021 3:59 PM, adrianv wrote:
> I think you need to give more information about what you're
trying to
> create. Is the shape defined by the dimensions of the
triangles? The
> space between them? Or maybe by some dimensions and some
angles? And
> then an altitude? Are the arcs circles? They don't look
like
it, so
> maybe not. What defines the arcs?
>
> I think knowing exactly what you're trying to create is an
important
> first step.
>
> Leea wrote
> I am sort of new and I manage to get along but
probably not
in the
> best
> or most efficient way. I marvel at some of the code I
see. I
want to
> create this and want to know the best way. All I come up
with is a
> series of thin triangles in a arc, each a different size.
How do I
> do it?
>
>
>
> thanks
> Lee
>
>
>
>
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Not exactly sure that I understand what you want.
This is another approach where I started with a cylinder and subtracted
the bits that I wanted to eliminate.
Perhaps with the right scaling and translating of the circle, you can
get the shape that you want.
It will not give you triangles at the edges but will give you a nice
concave pocket.
$fn=100;
height=20;
base=30;
difference(){
cylinder(h=height,r=base);
union(){
translate([-100,-50,-9]){cube([100,100,base]);}
translate([5,10,34]){scale([1,1.5,1]){sphere(r=35);}}
}
}
If this doesn't quite give you want you want, I hope it gives you some
more ideas about how to use difference and the other tools to make
something by subtracting shapes.
Ron
On 2021-02-25 11:15 p.m., Lee A wrote:
$fn=100;
height=20;
base=30;
for (i=[0:1:180]){
rotate ([0,0,-i]){
translate ([-base-3+(i/10),0,0])
rotate ([270,0,0]){
linear_extrude(height = 1, center = false, convexity = 10,
twist = 0)
polygon (points=[[0,0],[0,-height+(i/15)],[base-(i/10),0]]);
}
}
}
--
Ron Wheeler
Artifact Software
438-345-3369
rwheeler@artifact-software.com
I don't see what the problem is. All you need is the artistic vision of
Michelangelo and the mathematical capabilities of Laplace, then this
type of problem is trivial. However for the rest of us....
From your original (red?) image it looks as if it is half a cylinder,
with an the top sliced off at an angle. I would do that by making a
large cube, to slice the side off the cylinder, and rotate it to slice
off the top at an angle. If the top needs to be concave, then use a
large sphere to slice off the top. This is on the basis that if it looks
right, then it is right. If it is a one off, then nothing wrong with
getting the final shape you want by manually cutting/grinding. If the
exact shape is not necessary, then chase a shape you can more easily
generate.
On 26/02/2021 04:15, Lee A wrote:
1) No you don't have one. If you did it would be easier to describe.
Two of them pushed together (one a mirror image) would make sort of an
egg holder.
2) No
etc...
It should be emphasized that BOSL2 is a non-backwards-compatible rewrite of BOSL, and has become far more developed than the original BOSL library. BOSL2 code will not work with the original BOSL library. BOSL2 is still under development, but it’s in what I’d call BETA status.
You can find BOSL2 at https://github.com/revarbat/BOSL2/ https://github.com/revarbat/BOSL2/
- Revar
On Feb 25, 2021, at 8:22 PM, Lee A 683lee@337lee.com wrote:
Daniel was real close when he said amphitheater. I wish I had thought of that word, it would have saved a lot.
Adrianv, Yep, you got it, nailed it. I hadn't heard of BOSL so I have to research that. Thanks much. If I figure out BOSL I can make exactly what I want from your start.
Lee
On 2/25/2021 8:44 PM, adrianv wrote:
In OpenSCAD ultimately everything is a triangle. (Maybe you can make rectangles too?) There are no curves. So I'm not sure what you're hoping for about "something better than triangles". Do you mean for the end of the shape?
You said you want the hypotenuse a little concave? So here's a new version. My code is based on the BOSL2 library. You might be able to make a shape like this without a library by subtracting a sphere from a cylinder. It would be more symmetric, though. The outer arc of th shape produced by the code below is not a circle.
https://github.com/revarbat/BOSL2/wiki https://github.com/revarbat/BOSL2/wiki
include <BOSL2/std.scad>
include <BOSL2/skin.scad>
include <BOSL2/turtle3d.scad>
include <BOSL2/rounding.scad>
$fn=128;
width = 10;
height = 8;
curve=2; // Amount to curve hypotenuse inward
normal = line_normal([[-height,width],[0,0]]);
//triangle = [[-height,width],[0,0],[0,width]]; // Straight side triangle
triangle = [ each arc(points=[[-height,width], [-height,width]/2+normal*curve, [0,0]]),
[0,0],
[0,width]
];
trans = turtle3d([
["arc", 4, "right", 180, "shrink", 2]
],transforms=true);
sweep(triangle, trans);
Leea wrote
It is supposed to be 3D.
I would say the inverse of your image with the pointy tip on the
inside.
Take a bowl and pull/stretch the bottom center to the right side a
bit.
Then cut it in half vertically with the blade going left to right.
Trying to go from my mind to your mind without telepathy and not
coming
up with the right words.
How did you do your example? Maybe I can just reverse that.
I would like to smooth it by using something better than
triangles, some
shape I design with rounding.
Lee
On 2/25/2021 4:37 PM, adrianv wrote:
Your picture looked like a flat 2d picture of triangles and an arc.
So Is this sort of like what you're after?
Note: the triangles are coplanar but it doesn't look like it
because
of the shrinkage along the length which means the small one is not
aligned with the big one.
Leea wrote
It is defined by the dimensions of the triangles.
I am trying to figure out how to explain it. Imagine a
triangular
'rod'
that diminishes in size in all three dimensions from one end
to the
other. Then bend that rod into a U shape. So it is a solid
piece. The
inner arc is small and could be a circle. The outer arc is
almost
half a
circle but a bit elliptical. It could be circle if needed.
Ideally
the
hypotenuse would be a little concave but I was going to live
with
straight. I was hoping a picture was worth a lot of words.
Lee
On 2/25/2021 3:59 PM, adrianv wrote:
I think you need to give more information about what you're
trying to
create. Is the shape defined by the dimensions of the
triangles? The
space between them? Or maybe by some dimensions and some
angles? And
then an altitude? Are the arcs circles? They don't look
like
it, so
maybe not. What defines the arcs?
I think knowing exactly what you're trying to create is an
important
first step.
Leea wrote
I am sort of new and I manage to get along but
probably not
in the
best
or most efficient way. I marvel at some of the code I
see. I
want to
create this and want to know the best way. All I come up
with is a
series of thin triangles in a arc, each a different size.
How do I
do it?
thanks
Lee
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There is a simple way to construct your amphitheater with native modules:
--
Sent from: http://forum.openscad.org/
You are missing the desire that the hypotenuse of the triangle be curved---a
bowl shape. I think possibly subtracting a sphere from a cylinder may work
(as I suggested in my message) but it will not create a shape that is as
described because the curvature will be the same on both sides and the
outside shape will be circular, which is not what you get if you take a
tapered triangular prism and bend it in a U shape. So it depends on exactly
what the requirements for the shape are.
Parkinbot wrote
There is a simple way to construct your amphitheater with native modules:
--
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The ability to scale/distort the sphere prior to subtracting it from the
cylinder gives some more flexibility in the shape of the resulting
amphitheater.
On 2021-02-27 11:03 a.m., adrianv wrote:
You are missing the desire that the hypotenuse of the triangle be
curved---a bowl shape. I think possibly subtracting a sphere from a
cylinder may work (as I suggested in my message) but it will not
create a shape that is as described because the curvature will be the
same on both sides and the outside shape will be circular, which is
not what you get if you take a tapered triangular prism and bend it in
a U shape. So it depends on exactly what the requirements for the
shape are.
Parkinbot wrote
There is a simple way to construct your amphitheater with native
modules:
--
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That's true. But the outside boundary of the shape you get by bending the
rod is a spiral, not a simple transformation of a circle. You can make a
spiral edged "cylinder" using linear_extrude and trigonometry. But how do
you transform the sphere to align properly with a spiral edge? It's not at
all clear how you do that. I don't think it's going to be a linear
transformation.
There's a certain point where struggling to make the primitives do something
just doesn't make sense when you can directly do the thing you want with
"advanced" methods in a simple and straight forward way. This is part of
the reason why I'm interested in developing and implementing those
"advanced" methods: they may be difficult to implement but they aren't
necessarily "advanced" to use. For this problem a lot depends on the actual
goals of the original poster. Those goals were not clearly articulated.
Maybe subtracting a sphere from a cylinder is good enough. Maybe it's even
a better result, more closely aligned with the desires of the original
poster.
Here's an image of the bottom of the shape obtained by bending the tapered
rod:
http://forum.openscad.org/file/t2477/bottom.png
OpenSCAD mailing list-2 wrote
The ability to scale/distort the sphere prior to subtracting it from the
cylinder gives some more flexibility in the shape of the resulting
amphitheater.
On 2021-02-27 11:03 a.m., adrianv wrote:
You are missing the desire that the hypotenuse of the triangle be
curved---a bowl shape. I think possibly subtracting a sphere from a
cylinder may work (as I suggested in my message) but it will not
create a shape that is as described because the curvature will be the
same on both sides and the outside shape will be circular, which is
not what you get if you take a tapered triangular prism and bend it in
a U shape. So it depends on exactly what the requirements for the
shape are.
Parkinbot wrote
There is a simple way to construct your amphitheater with native
modules:
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It is always a question of the specification. In this case the TS gave a
drawing showing a kind of bagel with triangular crossections. If the spec
would show some curved sections, one would have to see, whether it could be
done with scaling al sphere or a rotate_extrude() ...
What I wanted to point out (with my last two posts) is that one should not
disregard the elegance of native solutions, especially when giving advice to
novice programmers.
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