Trying to emboss imported STL object using difference()
On 30.12.2020 20:01, donc wrote:
There must have been something wrong in the STL but I did a 3d print check
in Blender and it didn't find any non-manifold geometry. I went back and I
did get a console error but it had scrolled off the window. It was
ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion
violation! Expr: e_below != SHalfedge_handle() File:
/Users/kintel/code/OpenSCAD/libraries/install/include/CGAL/Nef_3/SNC_FM_decorator.h
Line: 427
I will go ahead and post the STL if you want to take a look.
logo.stl http://forum.openscad.org/file/t3066/logo.stl
Here's your STL repaired using polyfix, it works with your OpenSCAD code
now.
polyhedron 0 ==== volume=4446.65, dtol=0.01, atol=1e-06, maxiter=10
iteration 0: vertices=5256 faces=1752
warning: 18 zero area faces.
warning: nonmanifold edges: uc(1)=5256
merged 4360 vertices
removed 18 collapsed or zero area faces
split 17 faces
total changes=4395
no warnings
iteration 1: vertices=896 faces=1752
total changes=0
no warnings
Summary:
polyhedron 0: vertices=896 faces=1752 : no warnings
Carsten Arnholm
Carsten's fixed STL does work even though it has self-intersections:
But when looking at CGAL ERRORs,
The real lid is a polygon base which I extruded and added screw holes to.
All in OpenSCAD.
You could also have a bad polygon, they can also lead to CGAL ERRORs.
See https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#Mis-ordered_faces
But as you are extruding it prob. not, always worth a look with F12.
Your STL had self-intersections:
(top)
(bottom)
-----Original Message-----
From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of donc
Sent: Thu, 31 Dec 2020 06:01
Subject: Re: [OpenSCAD] Trying to emboss imported STL object using difference()
Wow! You had a very productive sleep.
This was a great idea. Soon as I started reading I thought it would work and
it did!
I was just trying to emboss the logo STL onto a standard cube for testing.
The real lid is a polygon base which I extruded and added screw holes to.
All in OpenSCAD.
There must have been something wrong in the STL but I did a 3d print check
in Blender and it didn't find any non-manifold geometry. I went back and I
did get a console error but it had scrolled off the window. It was
ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion
violation! Expr: e_below != SHalfedge_handle() File:
/Users/kintel/code/OpenSCAD/libraries/install/include/CGAL/Nef_3/SNC_FM_decorator.h
Line: 427
I will go ahead and post the STL if you want to take a look.
Anyway, I will add this projection trick to my mental OpenSCAD tool box.
BTW, I must say. I don't post often but I read a lot of computer forums and
you guys are the most helpful I have run across.
Thanks to everyone that answered.
Don
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I am not surprised that the logo STL had some issues. It was a PITA to create
and I had never done anything like that before.
I have never used polyfix. I will keep that in mind if I ever get another
suspect mesh.
I really like the projection, extrude method. That works like a champ since
this object has a uniform projection all along its height.
I went ahead and made that change in my program.
Thanks again.
Don
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You might want to look at Inkscape for tracing logos to create 2D figures, as
they are directly importable into OpenSCAD.
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On 30.12.2020 23:54, MichaelAtOz wrote:
Carsten's fixed STL does work even though it has self-intersections:
That's interesting. How does a triangle self-intersect?
Which software did you use to find/visualise self-intersections?
Carsten Arnholm
On 2020-12-31 12:35, Carsten Arnholm wrote:
On 30.12.2020 23:54, MichaelAtOz wrote:
Carsten's fixed STL does work even though it has self-intersections:
That's interesting. How does a triangle self-intersect?
Ok, I realise now it probably means partially overlapping triangles. If
so the mesh is no good.
Carsten Arnholm
Carsten, I used NetFabb, this one doesn't show on the MeshLab select/self-intersections.
This is the back face of your repaired STL.
Note in the red flagged section, the vertical line in the middle of the pink looks wobbly.
Similarly in the blue flagged section, but needs zoom to see.
Here I deleted the triangles on each side, there is a yellow line remaining.
Given your repair deletes zero area triangles, I imagine it is a needle like sliver,
where small number floats make it potentially break the surface around it.
I did similar in MeshLab, it also shows an extraneous line.
The tools I have and/or my driving skills can't drill deeper.
-----Original Message-----
From: Discuss [mailto:discuss-bounces@lists.openscad.org] On Behalf Of arnholm@arnholm.org
Sent: Thu, 31 Dec 2020 22:48
To: OpenSCAD general discussion
Subject: Re: [OpenSCAD] Trying to emboss imported STL object using difference()
On 2020-12-31 12:35, Carsten Arnholm wrote:
On 30.12.2020 23:54, MichaelAtOz wrote:
Carsten's fixed STL does work even though it has self-intersections:
That's interesting. How does a triangle self-intersect?
Ok, I realise now it probably means partially overlapping triangles. If
so the mesh is no good.
Carsten Arnholm
OpenSCAD mailing list
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