Mostly, just don't use $fn except to create regular polygons.  Use $fs and $fa; they are much less likely to lead you into silly settings.

You have $fn=16*360 = 5760.  Assuming that the units are millimeters, the model is about 100mm in diameter, so its circumference is 314mm.  That means that each side is 0.05mm.  Those tiny sides, and the even tinier artifacts that they might cause, might well be a key part of your geometry problems.  My bet is that you could use fewer than 100 sides and still be unable to see or feel the individual sides when you print it.  And if you can see them, bump it up to 300 or 500, and you've still got 10x fewer sides than your version does.

Preview is (at least for me) horribly laggy when you try to move it, and it has what look like convexity artifacts.

Removing all of the settings for $fn and adding in a single global setting for $fa=1 and $fs=1, and it previews fast and fixes the convexity artifacts.

The minimum settings that produced no micro flaws that I could see was
$fa = 1; $fs = 0.1;

On 10/27/2024 5:36 PM, Bob Carlson wrote:

What you can see on the screen is very different from what you can see in plastic.  Try some test prints.

Of course, I still like it to look nice and performance isn’t an issue.

Indeed, with Manifold performance is less of an issue than it once was.
But remember that spheres have a complexity that is the square of the
number of sides, so it can get unreasonable pretty fast.

I took my own advice, and did some test prints.  I'd done some in the
past, but not very systematically.

I made three cylinders, each with several vertical sections with different
numbers of sides.  One disk is 100mm in diameter, one 50mm, and one 25mm.
The two smaller ones have 25, 50, 100, and 150 sides; the larger one has
50, 100, 150, and 300 sides.  (I've enclosed the program below, for those
who might want to duplicate the experiment.)

Sides
Angle
Side length
25mm
50mm
100mm
25
14.4°
3.1mm
6.3mm

50
7.2°
1.6mm
3.1mm
6.3mm
100
3.6°
0.8mm
1.6mm
3.1mm
150
2.4°
0.5mm
1mm
2.1mm
300
1.2°

1mm

I've color-coded them red for obvious artifacts, yellow for subtle
artifacts, and green for no visible or feel-able artifacts.  Of course,
that's subjective, but it might give you an idea.

(For those who for whatever reason can't see the colors:  for the 25mm
cylinder the 25 is red and the rest are green. For the 50mm cylinder the 25
is red, 50 is yellow, and larger are green.  For the 100mm cylinder, 50 is
red and the others are green.)

I should probably do additional samples for larger and smaller cylinders,
but this is still interesting.

I was interested to see that the 50-gon was OK at a smaller size, but
increasingly bad as the size increased.  My intuition was that past some
size more sides doesn't help, because the angle between the sides is what
you'd perceive, but I don't seem to have found that size yet.

100mm isn't the largest circle I can print, and of course I can print arcs
that are arbitrarily large diameter, but this suggests that $fa=3 or so is
good enough for most things, and that $fs doesn't need to be less than
about 1.  $fa might need to be smaller for still-larger circles, and $fs
might need to be smaller for smaller circles.

Here's what the test cylinders look like:

Here's the test program:

include <BOSL2/std.scad>

// For the text
$fa = 2;
$fs = 1;

sides = [ 150, 100, 50, 25 ];
layerT = 6;        // Thickness of each layer
d = 50;            // Diameter
textT = 0.4;        // Thickness of text on the side
topTextT = 0.6;    // Thickness of text on the top
topTextSize = 6;    // Size of text on the top

// Draw a label wrapped around the cylinder
module clabel(text) {
path = up(layerT/2, path3d(reverse(circle(d=d))));
path_text(path, text, size=layerT0.8, textmetrics=true, valign="center", h=textT2+2, offset=-1, center=true);
}

for (i=[0:len(sides)-1]) translate([0,0,ilayerT]) {
fn = sides[i];
zcyl(d=d, h=layerT, anchor=BOTTOM, $fn=fn);
rotate(0) clabel(str(fn));
rotate(120) clabel(str(round(360/fn10)/10, "°"));
rotate(-120) clabel(str(round(PId/fn10)/10, "mm"));
}
up(len(sides)*layerT) text3d(str(d, "mm"), atype="ycenter", anchor=BOTTOM, h=topTextT, size=topTextSize);

OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

On 10/27/2024 5:36 PM, Bob Carlson wrote:

What you can see on the screen is very different from what you can see in plastic.  Try some test prints.

Of course, I still like it to look nice and performance isn’t an issue.

Indeed, with Manifold performance is less of an issue than it once was.
But remember that spheres have a complexity that is the square of the
number of sides, so it can get unreasonable pretty fast.

I took my own advice, and did some test prints.  I'd done some in the
past, but not very systematically.

I made three cylinders, each with several vertical sections with different
numbers of sides.  One disk is 100mm in diameter, one 50mm, and one 25mm.
The two smaller ones have 25, 50, 100, and 150 sides; the larger one has
50, 100, 150, and 300 sides.  (I've enclosed the program below, for those
who might want to duplicate the experiment.)

Sides
Angle
Side length
25mm
50mm
100mm
25
14.4°
3.1mm
6.3mm

50
7.2°
1.6mm
3.1mm
6.3mm
100
3.6°
0.8mm
1.6mm
3.1mm
150
2.4°
0.5mm
1mm
2.1mm
300
1.2°

1mm

I've color-coded them red for obvious artifacts, yellow for subtle
artifacts, and green for no visible or feel-able artifacts.  Of course,
that's subjective, but it might give you an idea.

(For those who for whatever reason can't see the colors:  for the 25mm
cylinder the 25 is red and the rest are green. For the 50mm cylinder the 25
is red, 50 is yellow, and larger are green.  For the 100mm cylinder, 50 is
red and the others are green.)

I should probably do additional samples for larger and smaller cylinders,
but this is still interesting.

I was interested to see that the 50-gon was OK at a smaller size, but
increasingly bad as the size increased.  My intuition was that past some
size more sides doesn't help, because the angle between the sides is what
you'd perceive, but I don't seem to have found that size yet.

100mm isn't the largest circle I can print, and of course I can print arcs
that are arbitrarily large diameter, but this suggests that $fa=3 or so is
good enough for most things, and that $fs doesn't need to be less than
about 1.  $fa might need to be smaller for still-larger circles, and $fs
might need to be smaller for smaller circles.

Here's what the test cylinders look like:

Here's the test program:

include <BOSL2/std.scad>

// For the text
$fa = 2;
$fs = 1;

sides = [ 150, 100, 50, 25 ];
layerT = 6;        // Thickness of each layer
d = 50;            // Diameter
textT = 0.4;        // Thickness of text on the side
topTextT = 0.6;    // Thickness of text on the top
topTextSize = 6;    // Size of text on the top

// Draw a label wrapped around the cylinder
module clabel(text) {
path = up(layerT/2, path3d(reverse(circle(d=d))));
path_text(path, text, size=layerT0.8, textmetrics=true, valign="center", h=textT2+2, offset=-1, center=true);
}

for (i=[0:len(sides)-1]) translate([0,0,ilayerT]) {
fn = sides[i];
zcyl(d=d, h=layerT, anchor=BOTTOM, $fn=fn);
rotate(0) clabel(str(fn));
rotate(120) clabel(str(round(360/fn10)/10, "°"));
rotate(-120) clabel(str(round(PId/fn10)/10, "mm"));
}
up(len(sides)*layerT) text3d(str(d, "mm"), atype="ycenter", anchor=BOTTOM, h=topTextT, size=topTextSize);

OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

PrusaSlicer has an Arc Fitting option that is default on in recent
versions.  It's not clear to me if it actually smooths the arcs (and
influences your results) or if the G2/G3 commands are just shorthand
for a large number of G1 commands. 

On 10/28/2024 3:31 AM, Dan Perry via Discuss wrote:

PrusaSlicer has an Arc Fitting option that is default on in recent
versions.  It's not clear to me if it actually smooths the arcs (and
influences your results) or if the G2/G3 commands are just shorthand for a
large number of G1 commands.

Hmm.  I did look for that, but for me it generated G1s.  I found the
option; it's disabled for me.

If it's generating a single G2/G3 for an arc, that's interpreted at the
printer and so can't be a shorthand for the original segments.  (Where
would the information about the segments be?)  The printer interprets it as
it chooses, probably close to its native resolution.

OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

How well the filament interpolates the curve depends on its viscosity
and the extrusion width. For example ABS smooths curves better than PLA.

How noticeable the facets are depends on how shiny the filament is as
you tend to notice the discontinuities in specular highlights more
than a subtle change in angle when looking from the edge.

I set $fs to half my extrusion width as it isn't really possible to
print details shorter than that and $fa to 6 for most things. I reduce
$fa if I am milling or printing things that have some aesthetic merit
rather than just functional.

Sounds like it would break polyholes which is what I use to get holes
the correct size.