Hello.

This is my first post. Started using OpenSCAD about a month ago and just ran
into a problem.

I was finishing up a sensor box lid for a non-profit I help out and was
going to emboss their logo. In the past, I had traced the 2d logo in Blender
and then gave it some height. In Blender I have taken this logo object and
used the boolean difference operation to "emboss" it.

I thought I would do the same in OpenSCAD so I imported the STL and tried to
do a difference(). It shows up correctly in preview but when I do a render
there isn't anything removed by the difference and I have the original
object.

I think it might be because there are multiple "pieces" in the logo. I tried
with a simple cylinder from Blender and was able to put a hole in the object
in OpenSCAD.

I am including an image showing the logo object after I imported the STL.

Thanks,

Don
http://forum.openscad.org/file/t3066/Screen_Shot_2020-12-29_at_1.png

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What does the console tell you?
Any error messages?

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Another option might be to import the 2D shape into OpenSCAD.

I'm not sure what Blender can export, OpenSCAD would need
either SVG or DXF (and is a bit picky about DXF).

ciao,
Torsten.

And yet another option is to use the extension Path to OpenSCAD from within Inkscape, although that opens up a whole new ball of wax, whatever that means. I use it frequently with great success. The extension creates polygon points based on the Inkscape vector image and the desired extrusion thickness. There's a scale factor in the resulting OpenSCAD code that has to be remarked out or set to one, else one gets too-small output.

On Tuesday, December 29, 2020, 7:39:01 PM EST, Torsten Paul <torsten.paul@gmx.de> wrote:  

Another option might be to import the 2D shape into OpenSCAD.

I'm not sure what Blender can export, OpenSCAD would need
either SVG or DXF (and is a bit picky about DXF).

ciao,
  Torsten.

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I have never used Blender to draw anything, but I used my CAD program (Auto
CAD) to sketch your logo and export as a DXF.  Having multiple objects in a
DXF has never caused me a problem unless they are not manifold.
http://forum.openscad.org/file/t1309/test.jpg

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Well, I slept on it and it came to me.

First, as someone pointed out, you may have a bad STL. You did not mention
the source of the lid, but if it's an STL, and you are trying to emboss one
stl into the other, one or both STLs may be the problem.

So here's something to try.
Import the logo.stl
make a projection of it
position and extrude it
difference or union that with the lid.

Here's a logo with multiple unconnected pieces put into and onto cubes.
You can just substitute your logo, and if it still fails to render, it is
likely because you are trying to emboss into a bad imported stl, in which
case, you should try to reproduce the lid with OpenSCAD.

Oh, and BTW, You can also drag and drop SVG files into OpenSCAD, and
Inkscape is your friend.
http://forum.openscad.org/file/t2121/Oilers_embossed.png
And the code to produce it...

module lid() {
translate([0,0,2])
color("blue",1)
cube([90,90,4],center=true);
}

module logo(){

translate([0,0,3])

	linear_extrude(2)
		projection()
			import("J:/Make/3D/Prints/Gifts/Oilers.stl");

}

difference(){
lid();
logo();
}

translate([95,0,0])
union(){
lid();
logo();
}

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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.
logo.stl http://forum.openscad.org/file/t3066/logo.stl

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 used your logo as is, commented out the linear_extrude() and projection(),
so it would just use the STL, and it worked fine.

There are only reason I can think of that might make it work on mine and not
on yours is that I am using OpenSCAD version 2020.12-RC3

Here's my modified code:

module lid() {
translate([0,0,2])
color("blue",1)
cube([90,90,4],center=true);
}

module logo(){
translate([0,0,6])
// linear_extrude(2)
// projection()
import("J:/Downloads/logo.stl");
}

difference(){
lid();
logo();
}

translate([95,0,0])
union(){
lid();
logo();
}

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Very interesting. I modified my program to try to difference and union the
logo straight from your STL.

I removed the linear_extrude and the projection in the logo module.

It failed to render the logo, and gave me an error:

ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion
violation! Expr: e_below != SHalfedge_handle()
File:
/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_3/SNC_FM_decorator.h
Line: 426, location unknown

Then I commented out the difference code.
It still failed to render the logo, and gave the same error.

Then I translated the logo high enough so that it did not intersect with the
cube, and leaving the difference code commented out, it still failed to
render the logo.

Then I tried reversing the order of the lid(); and logo(); in the union()
code.
That did not render the logo, but gave me the error.

Here's the final program in this test sequence. Render it, then chamge the
order of lid(); and logo(); in the union code. I am hoping that someone can
figure out why this error shows up in one case, and not the other.

module lid() {
translate([0,0,2])
color("blue",1)
cube([90,90,4],center=true);
}

module logo(){
translate([0,0,12])
// linear_extrude(2)
// projection()
color("yellow",1)
import("J:/Downloads/logo.stl");
}

//difference(){
// lid();
// logo();
// }

translate([95,0,0])
union(){
lid();
logo();
}

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