difference() not working as expected with rotate_extrude()
Hello!
I'm a novice OpenSCAD user, but not completely incompetent (or so I like to
think). I'm trying to difference a cube() with a rotate_extrude(), and I
expected the area of the cube within the torus to be differenced out. Am I
understanding something incorrectly here? I've used difference() many times
with cylinders, spheres, and other objects without issue. Using version
2018.01.06 (git 347eb1) under Windows. This is the code:
sides=360;
holder_width=28;
bolt_dia=16.66;
bolt_h_offset=5;
bolt_v_offset=16;
difference () {
translate ([0, -5.5, 0])
cube ([holder_width, 5.5, bolt_v_offset]);
translate ([bolt_h_offset + (bolt_dia / 2), -(5.5 / 2), bolt_v_offset])
#rotate ([270, 360 - 1, 0])
rotate_extrude (angle=180 + 2, convexity=10, $fn=sides)
translate ([5.55, 0, 0])
circle (d=5.55, $fn=sides);
}
I've increased the angle by 2 degrees and the circle diameter by a fraction
to make sure there's no actual way the area inside the torus can still be
connected to the rest of the piece. I was planning on union()'ing this
piece with another torus of the same size, because obviously the
difference() would leave the torus subtracted. I just hadn't gotten that
far yet because I can't make this work.
The net effect I'm going for is that this piece is a support for a
tailshaft. The tailshaft has a cutout that needs to rest on the inner part
of the torus, but the outside of the torus needs to fully supported to make
it printable. I may (probably!) be doing this the hard way, so I'm open to
better ways to do it.
Thanks!
--jc
Save a life; adopt a shelter animal.
http://forum.openscad.org/file/t824/cubeminustorus.png
Is this the result you experience, or is this the result you desire to
accomplish?
I did nothing to your code other than to reduce $fn to 60, as 360 means
excessive processing time and doesn't (shouldn't?) affect the final result.
I'm using 2017.1.20 on windows 7, which may be relevant if this is your
objective.
--
Sent from: http://forum.openscad.org/
No, what I want is to keep the yellow and red parts, and remove the blue
parts. Not sure if I'm doing this right to attach an image or not (it's
inlined in the email).
--jc
Save a life; adopt a shelter animal.
On Wed, Mar 21, 2018 at 10:52 AM, fred_dot_u fred_dot_u@yahoo.com wrote:
http://forum.openscad.org/file/t824/cubeminustorus.png
Is this the result you experience, or is this the result you desire to
accomplish?
I did nothing to your code other than to reduce $fn to 60, as 360 means
excessive processing time and doesn't (shouldn't?) affect the final result.
I'm using 2017.1.20 on windows 7, which may be relevant if this is your
objective.
--
Sent from: http://forum.openscad.org/
OpenSCAD mailing list
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http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
As the torus transversal section diameter is greater than the block width,
the difference will produce two separate parts. Is that what you want? If
so, it would be better to generate separately each part. For 3d printing
purposes, you may use a lower value of $fn with the benefit of a faster
render.
No, what I want is to keep the yellow and red parts, and remove the blue
parts. Not sure if I'm doing this right to attach an image or not (it's
inlined in the email).
To get it, difference the hull of the torus from the cube.
sides=60;
holder_width=28;
bolt_dia=16.66;
bolt_h_offset=5;
bolt_v_offset=16;
difference () {
translate ([0, -5.5, 0])
cube ([holder_width, 5.5, bolt_v_offset]);
hull() // <<<<<<<<<<<<<<<
translate ([bolt_h_offset + (bolt_dia / 2), -(5.5 / 2), bolt_v_offset])
#rotate ([270, 360 - 1, 0])
rotate_extrude (convexity=10, $fn=sides)
translate ([5.55, 0, 0])
circle (d=5.55, $fn=sides);
}
The addition of hull() gets much closer to what I want, except I want to
keep the torus itself. From the previous image, I want to keep the yellow
and red sections, and remove the blue.
--jc
Save a life; adopt a shelter animal.
On Wed, Mar 21, 2018 at 11:38 AM, Ronaldo Persiano rcmpersiano@gmail.com
wrote:
As the torus transversal section diameter is greater than the block width,
the difference will produce two separate parts. Is that what you want? If
so, it would be better to generate separately each part. For 3d printing
purposes, you may use a lower value of $fn with the benefit of a faster
render.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
This is horribly painful to render with $fn=360 (x seconds on a 6-core 3GHz
AMD), but is the end result I want (I know I can lower that for 3D
printing, of course). But there must be a better way?
sides=360;
holder_width=28;
bolt_dia=16.66;
bolt_h_offset=5;
bolt_v_offset=16;
module torus (fix=0) {
translate ([bolt_h_offset + (bolt_dia / 2), -(5.5 / 2), bolt_v_offset])
rotate ([270, 0, 0])
rotate_extrude (angle=180, convexity=10, $fn=sides)
translate ([5.5 + fix, 0, 0])
circle (d=5.5 + fix, $fn=sides);
}
difference () {
translate ([0, -5.5, 0])
cube ([holder_width, 5.5, bolt_v_offset]);
hull ()
torus ();
}
//
// Fix required, or complains that it's not manifold.
//
torus (0.01);
// 16 - 1 seconds
// 32 - 4 seconds
// 64 - 12 seconds
// 128 - 42 seconds
// 180 - 81 seconds
// 360 - 308 seconds (LOL, 2GiB memory!)
--jc
Save a life; adopt a shelter animal.
On Wed, Mar 21, 2018 at 11:50 AM, J.C. Wren jcwren@jcwren.com wrote:
The addition of hull() gets much closer to what I want, except I want to
keep the torus itself. From the previous image, I want to keep the yellow
and red sections, and remove the blue.
--jc
Save a life; adopt a shelter animal.
On Wed, Mar 21, 2018 at 11:38 AM, Ronaldo Persiano rcmpersiano@gmail.com
wrote:
As the torus transversal section diameter is greater than the block
width, the difference will produce two separate parts. Is that what you
want? If so, it would be better to generate separately each part. For
3d printing purposes, you may use a lower value of $fn with the benefit of
a faster render.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Is this what you want?
<pre> sides=36; holder_width=28; bolt_dia=16.66; bolt_h_offset=5; bolt_v_offset=16; difference () { translate ([0, -5.5, 0]) cube ([holder_width, 5.5, bolt_v_offset]); translate ([bolt_h_offset + (bolt_dia / 2), -(5.5 / 2), bolt_v_offset]) #rotate ([270, 360 - 1, 0]) difference() { cylinder(r=5.55,h=12,center=true); rotate_extrude (angle=180 + 2, convexity=10, $fn=sides) translate ([5.55, 0, 0]) circle (d=5.55, $fn=sides); } } </pre>--
Sent from: http://forum.openscad.org/
That is exactly what I'm looking for. Thank you :)
--jc
Save a life; adopt a shelter animal.
On Wed, Mar 21, 2018 at 12:41 PM, NateTG nate-openscadforum@pedantic.org
wrote:
Is this what you want?
<pre> sides=36; holder_width=28; bolt_dia=16.66; bolt_h_offset=5; bolt_v_offset=16; difference () { translate ([0, -5.5, 0]) cube ([holder_width, 5.5, bolt_v_offset]); translate ([bolt_h_offset + (bolt_dia / 2), -(5.5 / 2), bolt_v_offset]) #rotate ([270, 360 - 1, 0]) difference() { cylinder(r=5.55,h=12,center=true); rotate_extrude (angle=180 + 2, convexity=10, $fn=sides) translate ([5.55, 0, 0]) circle (d=5.55, $fn=sides); } } </pre>--
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