NetFabb tells me it has degenerate triangles near each eye, the nose and
the chin. It can remove them if you tell it to, it doesn't by default.

On 25 February 2018 at 16:09, jon jon@jonbondy.com wrote:

the prusa version of sli3r seems to be able to handle it, but I think I
can see the problem areas, either side of the nostrils there are two
holes after slicing, it may help you track down the issue...

On 25/02/18 16:09, jon wrote:

​
2018-02-25 13:34 GMT-03:00 Chris Camacho chris@bedroomcoders.co.uk:

You are right but I don't see how this could be indigestible to any
reasonable slicer.

​

​

Interesting.  When I look at the STL using NetFabb as a viewer, I don't
see holes (which is why I was mystified).  Both IdeaMaker and CraftWare
come up with bizarre slices (IdeaMaker does worse than CraftWare).  Here
is the IdeaMaker slice.  I would like to keep using IdeaMaker, so what I
was looking for was a way to modify/fix the STL.  The fact that I cannot
see the holes in NetFabb makes that difficult to do.

On 2/25/2018 11:34 AM, Chris Camacho wrote:

--
Sent from my desktop computer.
I do not receive emails while away from my desk,
nor do I receive texts on my main phone number
(which is a land line).
If you know that I am on the road, please text me.
If you know that I am home, please email me.

Very cool!

I can see where the slicer got confused.  There is that narrow part, and
with the spiral slicing, it needs to put two beads of filament where
there is barely room for one.  Still, I agree with the other comments
that a good slicer would work around the problem.  The IdeaMaker slicer
is set up to support the Raise3D N2 printer, so switching slicers would
involve a different kind of adventure.  Probably easier to tweak the STL.

Thanks for all of your help, and so quickly!   You guys rock!

Jon

On 2/25/2018 11:44 AM, fred_dot_u wrote:

--
Sent from my desktop computer.
I do not receive emails while away from my desk,
nor do I receive texts on my main phone number
(which is a land line).
If you know that I am on the road, please text me.
If you know that I am home, please email me.

On 25. feb. 2018 17:09, jon wrote:

Hi Jon,

Maybe this helps. I did a quick test and my utility found and fixed some
issues:

download link (2 day expiry)
https://www.expirebox.com/download/0bcbf69f4f408349b2b48b8605957954.html

More details in the log below

abm_polyfix -zip sample.stl

Parameters:
input_file = sample.stl
zip =

polyhedron 0 ================= volume=73528.4, dtol=0.01, atol=1e-06,
maxiter=10
iteration 0: vertices=249000 faces=83000
warning: 7 zero area faces.
warning: nonmanifold edges: uc(1)=249000
merged 207669 vertices
removed 343 collapsed or zero area faces
split 1 face
total changes=208013
no warnings

iteration 1: vertices=41331 faces=82658
merged 4 vertices
removed 8 collapsed or zero area faces
total changes=12
no warnings

iteration 2: vertices=41327 faces=82650
merged 2 vertices
removed 4 collapsed or zero area faces
total changes=6
no warnings

iteration 3: vertices=41325 faces=82646
total changes=0
no warnings

Summary:
polyhedron 0: vertices=41325 faces=82646 : no warnings

Writing: sample_polyfix.zip

... abm_polyfix finished, time used: 0d 00h 00m 05s

Regards
Carsten Arnholm

I don't think Netfab or any other software will be able to repair the
"holes" in your stl because the file represents a watertight model (with
some degenerated triangles). In fact, the holes are model genus like in a
torus or in a perforated cube. To repair it manually is a very hard task
due to the high number of triangles. So, either you regenerate the model
increasing its thickness (in such a way the negative mask doesn't touch the
positive one), or give up using spiral vase.

2018-02-25 13:45 GMT-03:00 jon jon@jonbondy.com:

Revising the model with Simplify3d, I can see the holes in it only after
slicing. It seems that the distance between the front and back surfaces in
those areas is much smaller than the filament thread diameter and the
slicer ignore them. Also, there is no observable holes when the model is
loaded in Sketchup (I load it with a fair scale up). So, it seems that
there is no genus in the model but a very very thin wall in some areas.

2018-02-25 19:16 GMT-03:00 Ronaldo Persiano rcmpersiano@gmail.com:

jon_bondy wrote

As Nophead said (his post was delayed, needing approval due to its size
BTW), NetFabb shows it has degenerate triangles. Unlike other issues, it
does not flag these with the big RED Cross.
You need to click on the Red Cross icon, make sure the check box is
selected, also press Update.

You see them as red lines:
http://forum.openscad.org/file/t359/jon_face_sample.jpg

These can generally be fixed (I've had ones it could not), via
Repair/Remove-Degenerated-Faces, I also do an auto repair after JIC.
Nopehead's post/email has the fixed STL attached.

BTW Jon, did you flatten the face to reduce overhangs?? Sorta looks that
way...

Admin - PM me if you need anything, or if I've done something stupid...

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. Obviously inclusion of works of previous authors is not included in the above.

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

Carsten:

That certainly did fix the problem!  Your tool gets better and better!

Thanks!

Jon

On 2/25/2018 3:26 PM, Carsten Arnholm wrote:

--
Sent from my desktop computer.
I do not receive emails while away from my desk,
nor do I receive texts on my main phone number
(which is a land line).
If you know that I am on the road, please text me.
If you know that I am home, please email me.

On 25/02/18 20:26, Carsten Arnholm wrote:

I guess I'm been asleep, which utility?

On 2018-02-26 10:31, Gadgetmind wrote:

It is a C++ utility I wrote (working name "abm_polyfix") for analyzing
and repairing polyhedra, reading from STL or AMF. It eliminates/merges
close vertices, eliminates zero area faces of various kinds, plus fixes
some non-manifold issues by splitting faces, etc.

Carsten Arnholm

On 26/02/18 10:36, arnholm@arnholm.org wrote:

Cool. Is it available for others to try? Linux friendly?

On 2018-02-26 11:51, Gadgetmind wrote:

The idea is to eventually provide a web service with this + more. This
is ongoing, if delayed. "abm_polyfix" runs on Windows and Linux like
everything I do.

In general I think the thread illustrates the somewhat fuzzy nature of
repairing problematic polyhedra in general and STL files in particular
(STLs do not provide any topology, it must be guessed). Several repair
tools exist but they appear to make different assumptions leading to
different results.

Carsten Arnholm

On 2/26/2018 7:41 AM, arnholm@arnholm.org wrote:

Are there other file formats that would be better?  Getting designers
like OpenSCAD and slicers to both implement something new would be
tough, but if there are clear benefits maybe it could be done.

On 26. feb. 2018 18:35, Jordan Brown wrote:

Yes, there are better formats (see below), but STL seems so entrenched
that it is very hard to get wide enough support for anything else. Some
requirements to a non-STL format I guess would be

1. Suited for polyhedron exchange between CAD applications, not just CAD
   to slicers.

2. Unambiguous format, with explicit topology

3. Efficient binary storage, plus equivalent ascii text version with
   same info. Binary/Ascii should be transparent to users.

4. It must be very simple.

etc.

OpenSCAD already support other 3D formats in addition to STL

OFF - http://paulbourke.net/dataformats/off/
AMF - https://en.wikipedia.org/wiki/Additive_Manufacturing_File_Format

Both of the above satisfy 1) and 2). AMF in its simplest form is quite
nice, but not terribly efficient, plus in my opinion it forgets 4) so it
will never become universal. OFF is a nice contender, but it does not
seem to be simple enough to be popular.

STL is both wasteful and ambiguous, it is just a sea of free floating
triangles. The binary format does not contain the same info as the text
format, etc. Its popularity is due to history only.

It seems to me super simplicity is a key. So any alternative format
should be even simpler than STL. Given that existing alternatives are
not very popular, we might as well propose something new to compete,
making simplicity the key feature while fixing some of the STL issues.
In my mind it could be something like

• simple file header to identify ASCII/Binary
• vertex coordinates stored only once
• triangle faces only
• faces defined by references to vertices, implicit normals

In other words, just the bare minimum, equivalent to the info that goes
into OpenSCAD polyhedron command. The text format would be more compact
than STL and simpler to read. The binary format would also be more
compact than STL since coordinates would be mentioned only once, and
therefore also not have any issues with interpretation.

You could say it is far too simple. But if you want it to be widely
adopted it must be extremely simple and fast. We could call it STL2 and
say it is how STL should have been defined in 1985 or so :-)

I don't have any illusions it would be successful, but if it was adopted
I think it would be helpful in avoiding some of the "damaged STL" issues
(not all) and enable easier sharing of models between various applications.

Just my thoughts, nothing else.

Carsten Arnholm

STL is unambiguous if it is written correctly and only used to represent a
manifold model with no self intersections. That is sufficient for 3D
printing as all 3D printed objects are manifold.

While other representations can also represent non-manifold objects it
pushes the problem downstream. How do you print a non-manifold object?

On 26 February 2018 at 19:44, Carsten Arnholm arnholm@arnholm.org wrote:

3MF is a superior alternative to AMF.

• It is less ambiguous, due to explicit rules on how to interpret certain
  non-manifold models that AMF leaves undefined. Specifically, it allows self
  intersection and overlapping triangles. Here's one reason why this is
  important. The union operation is not closed with respect to manifold
  meshes. If you union two manifold meshes, the result may not be manifold. I
  feel this is actually a defect in the definition of "manifold", because I
  think it's intolerable if you can't union two arbitrary shapes and be
  guaranteed to get a meaningful result. In any case, 3MF fixes this by
  defining the result of the union of two manifold meshes to be a valid 3MF
  model in all cases. AMF does not do this.
• 3MF is an open standard, and AMF is not (you have to pay money for a copy
  of the AMF standard, and you can't redistribute your copy of this secret,
  proprietary information.)
• 3MF has an open source library on github which interprets the standard.
• Nop head asks "how do you print a non-manifold object?". Well, the 3MF
  standard and the associated library implementation gives some unambiguous
  answers to that, for the cases that I mention above.

OpenSCAD has a 3MF implementation underway:
https://github.com/openscad/openscad/pull/1802.

The Cura slicer used to have an AMF implementation, but got rid of it, and
they now implement 3MF instead.

I feel it is not productive or useful at this point to design yet another
mesh file format.

On 26 February 2018 at 14:44, Carsten Arnholm arnholm@arnholm.org wrote:

I have never seen a physical solid object that isn't manifold. Surely that
is impossible, so if everything you can 3D print is manifold why do need to
represent non-manifolds. They only exist mathematically, not physically.

On 26 February 2018 at 20:36, Ronaldo Persiano rcmpersiano@gmail.com
wrote:

​
Consider two same axis cylinders joined end to end by an union operation.
If they have the same diameter, the union will be a longer cylinder. But if
the top cylinder should be 3D printed with a opaque filament and the bottom
one with a translucent one, the longer cylinder is not a good model for
printing it. We may want a two distinct volume with a common face. That is
not neither the union of two cylinders nor a manifold.

​I agree with you but 3D printing is not the only goal of CAD system in
general and of OpenSCAD in special. It would be legitimate to use OpenSCAD
for illustration, for instance. In an illustration of a car, why must the
motor hood have a thickness instead of being just the top hood surface?
Another non-manifold object.

Yes STL can't represent two manifolds touching but even if it could you
can't use it for multi-materials because there is no way to associate
properties. The simple solution is to use multiple STLs as I did nearly
nine years ago now
http://hydraraptor.blogspot.co.uk/2009/11/hacking-with-erik.html.

Yes STL is no good for illustrations or CAD interchange, it was only ever
intended for 3D printing.

On 26 February 2018 at 21:27, Ronaldo Persiano rcmpersiano@gmail.com
wrote:

​You are right saying that STL can't be used for multi-materials because
there is no way to associate properties. But it can represent
​
two manifolds touching. Given the STL of a cube, add two more triangles
subdividing the rectangle joining two opposed cube edges. If you want,
duplicate each of these triangles with opposed normals.

My point is: we need a model more general  than manifolds to comprise
things like multi-material 3D printing without hacked solutions. May be 3MF
is the solution.

On 2018-02-26 21:29, doug moen wrote:

That may be so. I agree that any proprietary nature of AMF is another
argument against it.

I had a very quick glance at the 3MF specs. The PDF is 50+ pages and
talks about many non-trivial aspects unrelated to the model itself.
Although it seems well documented, it does not quite meet my simplicity
requirement (#4). It is also XML based. I really like XML, but it means
it will not be super fast, and not compact.

There are very odd requirements in 3MF that the model must be in the
positive octant of the coordinate space. This tells me the format is not
generally intended for data exchange between application (failing my
#1), but probably intended specifically for 3d printers. So it isn't
what I had in mind.

Ok, I will be blunt and say this is likely to kill it as a useful format
for exchange. It will cause problems. Consider implementing a 3MF
importer in OpenSCAD.

union() {
cube(100);
translate([100,100,0])cube(100);
}

The above example will typically result in a model which is explicitly
not allowed in 3MF, unless you duplicate the common edge.

https://3mf.io/wp-content/uploads/2017/10/3MF_Core_Spec_v1.2_28129.pdf
page 28

Good point.

That's interesting.

My feeling is that if 3MF is the alternative, then STL will continue to
dominate due to its inertia. I may draft an alternative if nobody else
is interested. It will be either successful or ignored, so no harm done
:-) I guess 3MF will be useful for its purpose, but in my opinion there
should be a simpler and more compact alternative, and it isn't today's
STL.

Carsten Arnholm

On 26/02/18 22:59, nop head wrote:

I was musing on this recently.

I wanted to print a triangular prism on its side (toblerone!) with the
top flattened and a V notch then cut in this to let me stand a thin
object in it.

It wouldn't need any infill other than where the flat/notch on the top
was. I can design an object that's all the outside faces (with
thickness) and a support designed in, but would it actually work? Would
OpenSCAD cope/barf and would a slicer be happy with an object with
interior voids?

compact.

IIRC 3ML has a zip wrapper to make the XML compact. It won't be supper fast
though but compared to OpenSCAD rendering and slicer execution time, not to
mention 3D printing time, I doubt speed will be an issue.

On 27 February 2018 at 08:08, arnholm@arnholm.org wrote: