How to get at individual children?
Hello. I'm trying to write a module that will perform an operation on subsets
of its children. I tried using children() with an index, but this still
seems to give me all of the children. I'm seeing this behavior both with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the "first"
module to then ignore all of them except the first, so I expect to see only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried using
index=0 instead of just 0 as the parameter. Either way, the result is the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
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You ar enot doing anything wrong, there is an implicit union()
happening after for().
See the note here:
http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Conditional_and_Iterator_Functions#Intersection_For_Loop
And see this: https://github.com/openscad/openscad/issues/350
Miro Hrončok
Telefon: +420777974800
2015-02-24 0:02 GMT+01:00 xenomachina from-openscad@xenomachina.com:
Hello. I'm trying to write a module that will perform an operation on subsets
of its children. I tried using children() with an index, but this still
seems to give me all of the children. I'm seeing this behavior both with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the "first"
module to then ignore all of them except the first, so I expect to see only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried using
index=0 instead of just 0 as the parameter. Either way, the result is the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
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The problem is for always unions it children so there is only ever one
child of first() and that is the for() node.
On 23 February 2015 at 23:02, xenomachina from-openscad@xenomachina.com
wrote:
Hello. I'm trying to write a module that will perform an operation on
subsets
of its children. I tried using children() with an index, but this still
seems to give me all of the children. I'm seeing this behavior both with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the
problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the "first"
module to then ignore all of them except the first, so I expect to see only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried
using
index=0 instead of just 0 as the parameter. Either way, the result is the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
--
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http://forum.openscad.org/How-to-get-at-individual-children-tp11738.html
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Ah, I see. Thanks.
Is there any workaround for this behavior? I tried rebuilding OpenSCAD in
the issue350 branch and running it with the --enable=lazy-union flag, but
it still gives me 7 cylinders.
On Mon, Feb 23, 2015 at 3:07 PM, Miro Hrončok [via OpenSCAD] <
ml-node+s1091067n11739h62@n5.nabble.com> wrote:
You ar enot doing anything wrong, there is an implicit union()
happening after for().
See the note here:
And see this: https://github.com/openscad/openscad/issues/350
Miro Hrončok
Telefon: +420777974800
2015-02-24 0:02 GMT+01:00 xenomachina <[hidden email]
http:///user/SendEmail.jtp?type=node&node=11739&i=0>:
Hello. I'm trying to write a module that will perform an operation on
subsets
of its children. I tried using children() with an index, but this still
seems to give me all of the children. I'm seeing this behavior both with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a
build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the
problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the "first"
module to then ignore all of them except the first, so I expect to see
only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried
using
index=0 instead of just 0 as the parameter. Either way, the result is
the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
--
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No because children are not individual 3D objects, They are child nodes in
the syntax tree.
E.g.
child(1) {
a();
b();
c();
}
will select b(), which could generate many objects.
On 24 February 2015 at 20:53, xenomachina from-openscad@xenomachina.com
wrote:
Ah, I see. Thanks.
Is there any workaround for this behavior? I tried rebuilding OpenSCAD in
the issue350 branch and running it with the --enable=lazy-union flag, but
it still gives me 7 cylinders.
On Mon, Feb 23, 2015 at 3:07 PM, Miro Hrončok [via OpenSCAD] <[hidden
email] http:///user/SendEmail.jtp?type=node&node=11748&i=0> wrote:
You ar enot doing anything wrong, there is an implicit union()
happening after for().
See the note here:
And see this: https://github.com/openscad/openscad/issues/350
Miro Hrončok
Telefon: <a href="tel:%2B420777974800" value="+420777974800" target="_blank">+420777974800
2015-02-24 0:02 GMT+01:00 xenomachina <[hidden email]
http:///user/SendEmail.jtp?type=node&node=11739&i=0>:
Hello. I'm trying to write a module that will perform an operation on
subsets
of its children. I tried using children() with an index, but this still
seems to give me all of the children. I'm seeing this behavior both
with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a
build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the
problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the
"first"
module to then ignore all of them except the first, so I expect to see
only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried
using
index=0 instead of just 0 as the parameter. Either way, the result is
the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
--
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Yes, get that that's the behavior of for, though I honestly don't see how
the implicit union is desirable, except for backward compatibility.
What I'm asking is: how can I create a sequence of 3D objects in a loop,
and then iterate through them individually in a separate module? For
example, is there a way to get at the individual children of a union?
Here's a more concrete example of what I'd like to be able to do:
module hull_join() {
union() {
for_without_a_union (i=[0:$children - 2]) {
hull() {
children(index=i);
children(index=i+1);
}
}
}
}
hull_join() {
for_without_a_union(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
If for_without_a_union existed, then this would create a set of cylinders
in an arc and then hull_join would union together the hulls of each
adjacent pair producing a round arc path. See this combined screenshot:
https://imgur.com/MJjDlcY
To generate the left half of that screenshot I ended up manually unrolling
the loop, but I'm hoping there's a way to use/implement hull_join that
doesn't require unrolling loops, inlining the caller, or other sorts of
special-casing.
On Tue, Feb 24, 2015 at 12:59 PM, nophead [via OpenSCAD] <
ml-node+s1091067n11749h72@n5.nabble.com> wrote:
No because children are not individual 3D objects, They are child nodes in
the syntax tree.
E.g.
child(1) {
a();
b();
c();
}
will select b(), which could generate many objects.
On 24 February 2015 at 20:53, xenomachina <[hidden email]
http:///user/SendEmail.jtp?type=node&node=11749&i=0> wrote:
Ah, I see. Thanks.
Is there any workaround for this behavior? I tried rebuilding OpenSCAD in
the issue350 branch and running it with the --enable=lazy-union flag, but
it still gives me 7 cylinders.
On Mon, Feb 23, 2015 at 3:07 PM, Miro Hrončok [via OpenSCAD] <[hidden
email] http:///user/SendEmail.jtp?type=node&node=11748&i=0> wrote:
You ar enot doing anything wrong, there is an implicit union()
happening after for().
See the note here:
And see this: https://github.com/openscad/openscad/issues/350
Miro Hrončok
Telefon: <a href="tel:%2B420777974800" value="<a
href="tel:%2B420777974800" value="+420777974800" target="_blank">
+420777974800" target="_blank"><a href="tel:%2B420777974800" value="
+420777974800" target="_blank">+420777974800
2015-02-24 0:02 GMT+01:00 xenomachina <[hidden email]
http:///user/SendEmail.jtp?type=node&node=11739&i=0>:
Hello. I'm trying to write a module that will perform an operation on
subsets
of its children. I tried using children() with an index, but this
still
seems to give me all of the children. I'm seeing this behavior both
with
2013.01+dfsg-2.2 (the latest binary in the Ubuntu 14.04 repo) and a
build I
did myself from git commit 0dd3f004dd66798faef42ab4edaa72c12dc0ad66.
Here's a simplified version of what I'm trying that illustrates the
problem:
module first() {
child(0);
}
first() {
for(i=[0:20:120]) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
}
}
The for loop generates 7 cylinders in an arc. I would expect the
"first"
module to then ignore all of them except the first, so I expect to see
only
one cylinder. Instead I see all 7.
I have tried using children() instead of child() and I have also tried
using
index=0 instead of just 0 as the parameter. Either way, the result is
the
same (except some don't compile on the older OpenSCAD binary).
Any ideas what I'm doing wrong?
--
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Have you considered recursion? (I haven't for your particular issue, brain
not awake yet)
Unless specifically shown otherwise above, my contribution is in the Public Domain; To the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. This work is published globally via the internet. :) Inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/
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That's an interesting idea!
I just tried this...
module segment(i, step, last) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
if (i < last) segment(i + step, step, last);
}
hull_join() {
segment(0, 20, 120);
}
... and I still end up with something that looks a like the right image.
Something still seems to be making an implicit union. Is there some other
approach that could avoid this?
On Tue, Feb 24, 2015 at 2:27 PM, MichaelAtOz [via OpenSCAD] <
ml-node+s1091067n11751h34@n5.nabble.com> wrote:
Have you considered recursion? (I haven't for your particular issue, brain
not awake yet)
Unless specifically shown otherwise above, my contribution is in the
Public Domain; To the extent possible under law, I have waived all
copyright and related or neighbouring rights to this work. This work is
published globally via the internet. :)
Inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it!
http://www.ourfairdeal.org/
If you reply to this email, your message will be added to the discussion
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On Tue, Feb 24, 2015 at 04:35:30PM -0700, xenomachina wrote:
That's an interesting idea!
I just tried this...
module segment(i, step, last) {
rotate([0,0,i]) translate([10,0,0]) cylinder();
if (i < last) segment(i + step, step, last);
}
hull_join() {
segment(0, 20, 120);
}
... and I still end up with something that looks a like the right image.
Something still seems to be making an implicit union. Is there some other
approach that could avoid this?
This doesn't work with arbitrary 3D objects, but will do what you want from one
child and a series of transformations:
use <scad-utils/transformations.scad>
module hull_join (transformations)
{
for (i = [0 : len (transformations) - 2])
hull () {
multmatrix (transformations[i])
children ();
multmatrix (transformations[i + 1])
children ();
}
}
hull_join ([
for (i = [0 : 20 : 120])
rotation ([0, 0, i]) *
translation ([10, 0, 0])
])
cylinder (d = 1, h = 20);
--
Kind regards,
Loong Jin
Also worth looking at is generalized extrusion along path:
- https://github.com/openscad/openscad/issues/114
- https://github.com/openscad/list-comprehension-demos
--
Kind regards,
Loong Jin