here is the file...

Am Mo., 25. Mai 2020 um 23:08 Uhr schrieb dpa sc@pankd.de:

Congratulations! You have found a bug in the minkowski operator. That is
what I get with Thrown Together:

[image: image.png]

Yes, there is some reversed face in the minkowski! Just the minkowsky
renders fine but CGAL finds an error when it is boolean operated with the
connector. That face seems to be the cause.

I have never seen that bug before. The bug seems to be related to the
number of faces in the sphere and edges in the extrusion circle. Something
odd happens when both $fn are equal to 6.

Em seg., 25 de mai. de 2020 às 22:10, dpa sc@pankd.de escreveu:

why is there no error AND no output?

I get a CGAL error,

Rendering Polygon Mesh using CGAL...

ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion violation! Expr:
e->incident_sface() != SFace_const_handle() File:
/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h Line: 329

Geometries in cache: 8

Geometry cache size in bytes: 80896

CGAL Polyhedrons in cache: 1

CGAL cache size in bytes: 0

Total rendering time: 0 hours, 0 minutes, 0 seconds

Rendering finished.

If you missed that and tried F6 again, you don't get the error as the geometry is cached.

Whenever you have strange things like that it is good to try Design/Flush-cache.

Thank you, you have found a simple example of a bug I have seen hiding, where F5 then F6 has a CGAL
error, but F6 alone (fresh run or flush cache) does not, but the exported STL is bad.

A change in rotation will produce different angles where faces meet, sometimes they meet in a way
that is non-manifold, like an edge or point meeting exactly in the middle of a face.

But in this case I suspect a bug.

Interesting what I found inside (with add_rotate=7):

From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of dpa
Sent: Tue, 26 May 2020 07:09
To: discuss@lists.openscad.org
Subject: [OpenSCAD] rendering problem

Hey,

I was using OpenSCAD because it's so reliable, but yesterday I was very disappointed. I researched
the frequing same problem for almost exactly one day now and just couldn't get any further. There
are probably several in one.

For this question mail I didn't use my own polygons, just circle, rotate_extrude and minkowski with
a sphere.
The preview is fine, the rendering doesn't say enything but stays empty. Thats my first question:
why is there no error AND no output?
It brings an error when you change the "add_rotate" in cutomizer. What brings me to the 2nd
question: why does a rotation bring different errors?
And last but not least: how can I bring this object to render with a "add_rotate"=7 at all? Where
is the error / what I'm doing wrong?

best

Dietrich

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

BTW those inverted triangle z-fight when it is moved. I presume that means it is duplicated, one
correct, the other inverse.

From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of OzAtMichael
Sent: Tue, 26 May 2020 12:31
To: 'OpenSCAD general discussion'
Subject: Re: [OpenSCAD] rendering problem

why is there no error AND no output?

I get a CGAL error,

Rendering Polygon Mesh using CGAL...

ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion violation! Expr:
e->incident_sface() != SFace_const_handle() File:
/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_S2/SM_const_decorator.h Line: 329

Geometries in cache: 8

Geometry cache size in bytes: 80896

CGAL Polyhedrons in cache: 1

CGAL cache size in bytes: 0

Total rendering time: 0 hours, 0 minutes, 0 seconds

Rendering finished.

If you missed that and tried F6 again, you don't get the error as the geometry is cached.

Whenever you have strange things like that it is good to try Design/Flush-cache.

Thank you, you have found a simple example of a bug I have seen hiding, where F5 then F6 has a CGAL
error, but F6 alone (fresh run or flush cache) does not, but the exported STL is bad.

A change in rotation will produce different angles where faces meet, sometimes they meet in a way
that is non-manifold, like an edge or point meeting exactly in the middle of a face.

But in this case I suspect a bug.

Interesting what I found inside (with add_rotate=7):

From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of dpa
Sent: Tue, 26 May 2020 07:09
To: discuss@lists.openscad.org
Subject: [OpenSCAD] rendering problem

Hey,

I was using OpenSCAD because it's so reliable, but yesterday I was very disappointed. I researched
the frequing same problem for almost exactly one day now and just couldn't get any further. There
are probably several in one.

For this question mail I didn't use my own polygons, just circle, rotate_extrude and minkowski with
a sphere.
The preview is fine, the rendering doesn't say enything but stays empty. Thats my first question:
why is there no error AND no output?
It brings an error when you change the "add_rotate" in cutomizer. What brings me to the 2nd
question: why does a rotation bring different errors?
And last but not least: how can I bring this object to render with a "add_rotate"=7 at all? Where
is the error / what I'm doing wrong?

best

Dietrich

<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_con
tent=emailclient>

Virus-free.
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_con
tent=emailclient> www.avg.com

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

It works fine for me if I flush the cache before F6 but not if I do F5, F6.
So it is not a bug in Minkowski, it is just the normal PolySet grid snap
bug that breaks topology and caches it.

On Tue, 26 May 2020 at 04:15, OzAtMichael oz.at.michael@gmail.com wrote:

nophead wrote

I'm not so sure.
As I said, z-fighting outside-face & inside-face.
In Netfabb I was able to delete the wrong face, and the right one was then
exposed.
I'm still looking, but it does look like duplicated faces.

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

• click on my MichaelAtOz label, there is a link to email me.

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.

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

As long as I flush the cache and do F6 it all looks fine to me and I can
export the STL to Netfabb and that says it's fine as well.

On Tue, 26 May 2020 at 11:41, MichaelAtOz oz.at.michael@gmail.com wrote:

On 2020-05-26 00:06, Ronaldo Persiano wrote:

Could be an intermittent problem, or behaviour depends on version of
OpenSCAD and/or operating system. It is not necessarily minkowski that
fails, since difference is the final operation.

I tried with OpenSCAD 2017.01.20 under Win10 and it shows no obvious
problems (but see below), it is reported as

Total rendering time: 0 hours, 0 minutes, 10 seconds
Top level object is a 3D object:
Simple:        yes
Vertices:      369
Halfedges:    1556
Edges:        778
Halffacets:    826
Facets:        413
Volumes:        3
Rendering finished.
STL export finished.

However, testing the exported STL in polyfix reveals a higher number of
faces (628) compared to what OpenSCAD reports (413), which is kind of
strange.

polyhedron 0 ================= volume=1469.81, dtol=0.01, atol=1e-06,
maxiter=10
iteration 0: vertices=1884 faces=628
warning: 4 zero area faces.
warning: nonmanifold edges: uc(1)=1884
merged 1574 vertices
removed 16 collapsed or zero area faces
removed 2 duplicate faces
removed 2 nonmanifold faces
total changes=1594
no warnings

iteration 1: vertices=310 faces=608
removed 2 unused vertices
total changes=2
no warnings

iteration 2: vertices=308 faces=608
total changes=0
no warnings

Summary:
polyhedron 0: vertices=308 faces=608 : no warnings

When instead exporting the same model from OpenSCAD to OFF format, it
showed an even higher number of faces (710):

polyhedron 0 ================= volume=1469.81, dtol=0.01, atol=1e-06,
maxiter=10
iteration 0: vertices=359 faces=710
warning: 86 zero area faces.
merged 49 vertices
removed 98 collapsed or zero area faces
removed 2 duplicate faces
removed 2 nonmanifold faces
total changes=151
no warnings

iteration 1: vertices=310 faces=608
removed 2 unused vertices
total changes=2
no warnings

iteration 2: vertices=308 faces=608
total changes=0
no warnings

Summary:
polyhedron 0: vertices=308 faces=608 : no warnings

As you can see, polyfix resolved both of the above to vertices=308
faces=608, even if the starting points were different. I think this
shows that at least part of the problems lie in file export code.

It does not make sense that the number of faces exported depends on the
file format chosen. Clearly, there is no check for zero area faces on
file export in OpenSCAD.

I also tried this, which seemed to work
https://gist.github.com/arnholm/de50168cd1a477be1de116e100a8066a

Carsten Arnholm

All well & good, but F5+F6 should work.

It needs to be fixed.

Your render() based designs are probably prone to this issue.

In this specific case, Flush Cache & F6 & Export STL, produced a broken STL, that one on the
Netfabb images above.

From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of nop head
Sent: Tue, 26 May 2020 21:03
To: OpenSCAD general discussion
Subject: Re: [OpenSCAD] rendering problem

As long as I flush the cache and do F6 it all looks fine to me and I can export the STL to Netfabb
and that says it's fine as well.

On Tue, 26 May 2020 at 11:41, MichaelAtOz oz.at.michael@gmail.com wrote:

nophead wrote

I'm not so sure.
As I said, z-fighting outside-face & inside-face.
In Netfabb I was able to delete the wrong face, and the right one was then
exposed.
I'm still looking, but it does look like duplicated faces.

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

• click on my MichaelAtOz label, there is a link to email me.

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.

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

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

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