Voxel file format

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Ivo
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Voxel file format

Ivo
Shapeways has a an upper limit of 1000000 polygons per model.

A format that does not seem to have this limitation us the SVX format :
http://www.shapeways.com/blog/archives/17972-shapeways-launches-svx-voxel-file-format-for-3d-printing.html
described in : http://abfab3d.com/svx-format/

Sculpteo is less specific ; "tiny details in large files with excessive numbers of polygons will not be rendered"

How hard would it be be to build an exporter for this format ?

SVX seems to be very poorly supported.
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Re: Voxel file format

QuackingPlums
I can't speak for Shapeways but my RepRap is unlikely to have sufficient resolution to print 1,000,000 faces on an object the size of my print bed (and for those faces to be distinguishable).

A better approach might be to work out the limitations of your print format and output the correct resolution to match. There will be no discernible different and file sizes will be smaller.
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threads

yvette
In reply to this post by Ivo
hi all,

i'm trying to "cut" threads in openSCAD.  i'm using the threads.scad
module i found on thingiverse, like so:

use <threads.scad>;
...
english_thread(diameter=(632ScrewRadius*2),
threads_per_inch=32,
length=(coverDepth+coverThickness),
internal=true,
$fn=30);

gosh, is it *slow*!  i played a game of freecell and the progress meter
hasn't budged from "just started".  and now i've finished typing this
email and still no progress.

i put cylinders in the code to check for positioning and depth; once i
got those right, i commented out ONLY the first cylinder and inserted
just the code for the one thread above.  my res time (F6) was 45sec; now
it could be hours.  from *one* thread - and i have four to gen before
slicing.

i'm sure the lack of progress is due to threads.scad creating a
bazillion polygons.  i'm not trying to complain; i'm just trying to get
my stuff printed.

is there any alternative to threads.scad?

thanks!
yvette

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Ivo
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Re: Voxel file format

Ivo
In reply to this post by QuackingPlums
QuackingPlums wrote
I can't speak for Shapeways but my RepRap is unlikely to have sufficient resolution to print 1,000,000 faces on an object the size of my print bed (and for those faces to be distinguishable).
Models like
https://www.shapeways.com/product/KPZ4NZLQH/twisty-cube?li=search-results-5&optionId=42490374

https://www.shapeways.com/product/TCAXXR9BJ/woven-purse?li=search-results-30&optionId=42445606

Will get to a million faces.
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Re: Voxel file format

kintel
Administrator
In reply to this post by Ivo
On Apr 23, 2015, at 08:36 AM, Ivo <[hidden email]> wrote:

> http://www.shapeways.com/blog/archives/17972-shapeways-launches-svx-voxel-file-format-for-3d-printing.html
> described in : http://abfab3d.com/svx-format/
>
Do shapeways have a limitation on the size of SVX files?
Such voxel files will easily reach a GB of raw data..

 -Marius


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Re: Voxel file format

Ivo
kintel wrote
On Apr 23, 2015, at 08:36 AM, Ivo <[hidden email]> wrote:

> http://www.shapeways.com/blog/archives/17972-shapeways-launches-svx-voxel-file-format-for-3d-printing.html
> described in : http://abfab3d.com/svx-format/
>
Do shapeways have a limitation on the size of SVX files?
Such voxel files will easily reach a GB of raw data..

 -Marius
With the existing png export it almost seems like something that can be scripted together in a sunday afternoon.
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Re: Voxel file format

nophead
Might take more than an afternoon to run though as you would need to slice with projection() and that isn't quick.

On 23 April 2015 at 21:08, Ivo <[hidden email]> wrote:
kintel wrote
> On Apr 23, 2015, at 08:36 AM, Ivo &lt;

> ivo.knutsel@

> &gt; wrote:
>
>> http://www.shapeways.com/blog/archives/17972-shapeways-launches-svx-voxel-file-format-for-3d-printing.html
>> described in : http://abfab3d.com/svx-format/
>>
> Do shapeways have a limitation on the size of SVX files?
> Such voxel files will easily reach a GB of raw data..
>
>  -Marius

With the existing png export it almost seems like something that can be
scripted together in a sunday afternoon.



--
View this message in context: http://forum.openscad.org/Voxel-file-format-tp12468p12473.html
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Re: Voxel file format

stonysmith
First, it's 1million TRIANGLES, not 1m polygons.  If you upload a file made out of polygons, it will first be triangulated, and then fail in the upload process for having more than the limit of triangles.

Second, I believe that, rather silently, they upped it to TWO million triangles many months ago. (or, at least some number more than 1m)

Third, the Shapeways file size limit is still 64mb.  But, SVX must be zipped, so the compression will help you out on the size.

Forth, I'm not real happy with the SVX implementation, the model is uploaded as voxels (cubes), but they render them out to polygons, and then apply a polygon reduction operation to the outer shell of the model.  The polygon reduction they apply has the effect of smoothing the model a bit too much for my tastes.  It may well be within the resolution of the printer, but to me the detail produced looks terrible.
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Re: Voxel file format

kintel
Administrator
On Apr 23, 2015, at 21:00 PM, stonysmith <[hidden email]> wrote:

> […] The polygon
> reduction they apply has the effect of smoothing the model a bit too much
> for my tastes.  It may well be within the resolution of the printer, but to
> me the detail produced looks terrible.
>
That’s good feedback.
Perhaps a much better solution would be for OpenSCAD to perform said polygon reduction on the original design. As OpenSCAD tends to generate a lot of tiny polygons, we could probably reduce typical designs significantly before it having a large visual impact.

 -Marius


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Re: Voxel file format

clothbot

On Apr 23, 2015, at 10:00 PM, Marius Kintel <[hidden email]> wrote:

On Apr 23, 2015, at 21:00 PM, stonysmith <[hidden email]> wrote:

[…] The polygon
reduction they apply has the effect of smoothing the model a bit too much
for my tastes.  It may well be within the resolution of the printer, but to
me the detail produced looks terrible.

That’s good feedback.
Perhaps a much better solution would be for OpenSCAD to perform said polygon reduction on the original design. As OpenSCAD tends to generate a lot of tiny polygons, we could probably reduce typical designs significantly before it having a large visual impact.

CGAL does document some mesh reduction approaches:


Andrew.


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Re: threads

Chow Loong Jin
In reply to this post by yvette
On Thu, Apr 23, 2015 at 08:16:08AM -0700, Yvette S. Hirth, CCP, CDP wrote:

> hi all,
>
> i'm trying to "cut" threads in openSCAD.  i'm using the threads.scad module
> i found on thingiverse, like so:
>
> use <threads.scad>;
> ...
> english_thread(diameter=(632ScrewRadius*2),
> threads_per_inch=32,
> length=(coverDepth+coverThickness),
> internal=true,
> $fn=30);
>
> gosh, is it *slow*!  i played a game of freecell and the progress meter
> hasn't budged from "just started".  and now i've finished typing this email
> and still no progress.
>
> i put cylinders in the code to check for positioning and depth; once i got
> those right, i commented out ONLY the first cylinder and inserted just the
> code for the one thread above.  my res time (F6) was 45sec; now it could be
> hours.  from *one* thread - and i have four to gen before slicing.
>
> i'm sure the lack of progress is due to threads.scad creating a bazillion
> polygons.  i'm not trying to complain; i'm just trying to get my stuff
> printed.
>
> is there any alternative to threads.scad?
Use OpenSCAD 2015.03 and threads.scad from MCAD's dev branch. It's an updated
version of the threads.scad you're using. Uses list comprehension, and sweep()
for generalized extrusion of the threads, and is much faster than the
implementation you're using.

--
Kind regards,
Loong Jin

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Re: threads

Chow Loong Jin

On Fri, Apr 24, 2015 at 12:13:00PM +0800, Chow Loong Jin wrote:

> On Thu, Apr 23, 2015 at 08:16:08AM -0700, Yvette S. Hirth, CCP, CDP wrote:
> > hi all,
> >
> > i'm trying to "cut" threads in openSCAD.  i'm using the threads.scad module
> > i found on thingiverse, like so:
> >
> > use <threads.scad>;
> > ...
> > english_thread(diameter=(632ScrewRadius*2),
> > threads_per_inch=32,
> > length=(coverDepth+coverThickness),
> > internal=true,
> > $fn=30);
> >
> > gosh, is it *slow*!  i played a game of freecell and the progress meter
> > hasn't budged from "just started".  and now i've finished typing this email
> > and still no progress.
> >
> > i put cylinders in the code to check for positioning and depth; once i got
> > those right, i commented out ONLY the first cylinder and inserted just the
> > code for the one thread above.  my res time (F6) was 45sec; now it could be
> > hours.  from *one* thread - and i have four to gen before slicing.
> >
> > i'm sure the lack of progress is due to threads.scad creating a bazillion
> > polygons.  i'm not trying to complain; i'm just trying to get my stuff
> > printed.
> >
> > is there any alternative to threads.scad?
>
> Use OpenSCAD 2015.03 and threads.scad from MCAD's dev branch. It's an updated
> version of the threads.scad you're using. Uses list comprehension, and sweep()
> for generalized extrusion of the threads, and is much faster than the
> implementation you're using.
Oh, it also obeys $fs, $fa and $fn, so you'll have to tweak those values for
higher faceting resolution on small diameters. OpenSCAD's default $fs, $fa and
$fn parameters are unfortunately pretty coarse.

--
Kind regards,
Loong Jin

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Re: Voxel file format

nophead
In reply to this post by clothbot
>As OpenSCAD tends to generate a lot of tiny polygons

Really, I thought it just generated the polygons implied by the source code with $fn, etc. Does it make some extra ones up?

On 24 April 2015 at 03:59, Andrew Plumb <[hidden email]> wrote:

On Apr 23, 2015, at 10:00 PM, Marius Kintel <[hidden email]> wrote:

On Apr 23, 2015, at 21:00 PM, stonysmith <[hidden email]> wrote:

[…] The polygon
reduction they apply has the effect of smoothing the model a bit too much
for my tastes.  It may well be within the resolution of the printer, but to
me the detail produced looks terrible.

That’s good feedback.
Perhaps a much better solution would be for OpenSCAD to perform said polygon reduction on the original design. As OpenSCAD tends to generate a lot of tiny polygons, we could probably reduce typical designs significantly before it having a large visual impact.

CGAL does document some mesh reduction approaches:


Andrew.


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Re: Voxel file format

kintel
Administrator
On Apr 24, 2015, at 06:17 AM, nop head <[hidden email]> wrote:

> >As OpenSCAD tends to generate a lot of tiny polygons
>
> Really, I thought it just generated the polygons implied by the source code with $fn, etc. Does it make some extra ones up?
>
During CSG operations, tiny polygons tend to be introduced by CGAL, partially due to their infinite precision. Some of these polygons could easily be reduced to nothing by employing a topology-preserving optimization mechanism.

 -Marius


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