Does that imply that there will be fillets on those inside concave edges?

On Mon, Jun 22, 2026 at 9:13 AM Bob Roos via Discuss <
discuss@lists.openscad.org> wrote:

Hi Leonard,

no I just want the outside edges to be rounded.

Monday, June 22, 2026, 10:34:31 AM, you wrote:

--
have Fun,
Bob                          mailto:roosbob@wybatap.com

Rounding this is not particularly simple.  If you want to do it the way you
started out, by subtracting a suitable cuboid:

r=1;
diff()
cuboid([30,10,16],rounding=r)
position(LEFT) tag("remove")
cuboid([3,10,6],anchor=LEFT)

edge_profile_asym(except=[LEFT+FWD,LEFT+BACK,RIGHT+BOT,RIGHT+TOP],flip=true,corner_type="round",size=[r,r])
xflip()mask2d_roundover(r=r);

You have to use edge_profile_asym to place the roundings on the cube when
you want more complicated arrangements of roundings.

I think it's somewhat easier to do it with round_prism:

base = difference([
rect([30,16],anchor=LEFT),
rect([3,6], anchor=LEFT)
]);
rounded_prism(base[0], height=10,joint_top=1, joint_bot=1,
joint_sides=[1,1,1,0,0,1,1,1],k=.9);

On Mon, Jun 22, 2026 at 12:58 PM Bob Roos via Discuss <
discuss@lists.openscad.org> wrote:

Hi Adrian,

I knew it wasn't simple.  I will study your examples.

I did get what I wanted with this.  It took a lot of trial and error to figure out where left and right top and bottom were

include <BOSL2/std.scad> //or screws or threading
$fn=24;
Inch=25.4;
LHF = .28;      // Layer height for faster build
LH=.25; // Layer height after 1st layer
FL=.2; // first layer

L = 7 * Inch;
L1 = 1 * Inch;
L2 = 3.5 * Inch;
W = Inch;
D = .5 * Inch;
D1 = .25 * Inch;
T = 3;

difference(){
Block();
right(T/2) down(3) Notch(T/2,3,W,.25Inch);
right(L-T/2) down(3) rotate([0,0,180])Notch(T/2,3,W,.25Inch);
up(D1-1)#right(36)linear_extrude(1)text("Super Nifty Window Prop",anchor=TOP+LEFT,size=8,valign="bottom");
}

module Block(){
cuboid([L,W,D1],rounding=T/2,anchor=BOT+LEFT) ;  // full blockshow_anchors()
up(T)cuboid([L1,W,D+T],rounding=T/2,anchor=TOP+LEFT,except=TOP);
up(T)right(L)cuboid([L2,W,D+T],rounding=T/2,anchor=TOP+RIGHT,except=TOP);
up(T)right(30)cuboid([L1,W,D+T],rounding=T/2,anchor=TOP+LEFT,except=TOP);
up(T)right(60)cuboid([L1,W,D+T],rounding=T/2,anchor=TOP+LEFT,except=TOP);
}

module Notch(R,XX,YY,ZZ){
Dx=XX;
Dy=YY;
Dz=ZZ;

cuboid([XX,YY,ZZ]){
*  position(RIGHT+FRONT)rounding_edge_mask(r=R,h=Dz);
*  position(RIGHT+BACK) rounding_edge_mask(r=R,h=Dz,spin=270);

     position(TOP+FRONT)  rounding_edge_mask(r=R,h=Dx,orient=LEFT,spin=0);
     position(BOT+FRONT)  rounding_edge_mask(r=R,h=Dx,orient=LEFT,spin=90);
    
     position(TOP+LEFT)   rounding_edge_mask(r=R,h=Dy,orient=FRONT);
  *   position(TOP+RIGHT)  rounding_edge_mask(r=R,h=Dy,orient=FRONT);
    
     position(BOT+LEFT)   rounding_edge_mask(r=R,h=Dy,orient=FRONT,spin=270);

•  position(BOT+RIGHT)  rounding_edge_mask(r=R,h=Dy,orient=FRONT);
  

• position(BACK+RIGHT) rounding_edge_mask(r=R,h=Dz);
  

*    position(BACK+LEFT)  rounding_edge_mask(r=R,h=Dz);
    
     position(BOT+BACK)   rounding_edge_mask(r=R,h=Dx,orient=RIGHT,spin=270);
     position(TOP+BACK)   rounding_edge_mask(r=R,h=Dx,orient=RIGHT,spin=180);
}

Monday, June 22, 2026, 4:38:46 PM, you wrote:

--
have Fun,
Bob                          mailto:roosbob@wybatap.com

On 6/22/2026 7:13 AM, Bob Roos via Discuss wrote:

TL;DR:  use $fn for regular polygons, and set it on the individual call;
for circular things just set $fa and $fs to 1 at the top level.

I recommend against using $fn like this.  $fn's behavior is obvious, but
it often produces results that are more complex than they need to be. 
It is very easy to end up with models that are unnecessarily complex,
causing performance problems for OpenSCAD itself and perhaps for
downstream tools.  The picture is worse for spheres, because there the
number of sides is $fn^2/2.  Use $fn only when you need to control the
exact number of sides, which is mostly when you want to create a regular
polygon - and there, you almost always want to set $fn on the particular
call, not using a regular assignment.

Setting $fn to 72, a 72-gon, is pretty good up to a  diameter of a
hundred mm or so, depending on your tastes, but if you get down to a
diameter of a millimeter you've got sides that are only 0.05 mm, smaller
than the precision of your printer.

Much better is to use $fa and $fs, or in recent builds the experimental
$fe, to control your circles, because they automatically adjust for the
size of the circle.  Mostly, you can set them once, set them the same
for all models, and be happy.

I usually set both $fs and $fa to 1.  For 1mm-diameter circles, that
yields a pentagon; for 100mm diameter circles it yields a 315-gon.  If
you want to tune a bit better, you might set $fa larger (because a
315-gon is more than you need for most purposes) and $fs smaller (if you
really need your tiny circles to be more precise).

A while back I wrote a demo program, attached, that generates cylinders
and arcs with adjustable sizes and numbers of sides, so that I could see
and feel how the various parameters ended up.  I printed samples ranging
from a 10mm diameter circle to a 1000mm diameter arc.  At 10mm I cannot
see or feel the sides of a 25-gon; at 1000mm I cannot see or feel the
sides of a 300-gon.

In a recent post I advocated against attach() as the first option you
consider for positioning child objects and in particular I dismissed using
edges as attachment sites, but if you want to put edge masks on a cube,
this is exactly the situation where you want to do these things.  Something
like diff() attach(LEFT+RIGHT, LEFT+FWD, inside=true)
rounding_edge_mask(...) can be exactly the trick with less trial and
error.  For placing a fillet use inside=false and then
yrot(90)fillet(...).

On Mon, Jun 22, 2026 at 5:42 PM Bob Roos via Discuss <
discuss@lists.openscad.org> wrote: