Re: [OpenSCAD] Newbie Hull problem
On 1/28/2018 12:14 PM, Jordan Brown wrote:
On 1/28/2018 11:46 AM, MDFChris wrote:
I've just started using OpenSCAD and so far I'm liking it, it suits my
engineering mind however I'm having an issue with a simple hull ?
I'm designing a nozzle for my 3D printer which seems simple enough using a
difference of two'd hull'd cubes:
//Nozzle
nozzle();
module nozzle(){
difference(){
port(1);
port(0);
}
}
module port(d){
hull() {
cube([19.5+d2,15+d2,2],center=true);
translate([-10,4,15])
rotate([0,-45,0])
cube([7+d2,14+d2,2],center=true);
}
}
however if I increase the rotation angle of the outlet port beyond -45 (i.e.
-50 or more) the open end starts to close up ?, I can't figure if I'm doing
something wrong or is this some sort of rounding error ?
It looks like your two top-end cubes have their top faces in the same
place. This causes an effect called Z-fighting, where the rendering
program can't quite decide whether or not there's something there.
Note the shimmery yellow/green nature of that area; you don't want
that. At the higher angles it does indeed look like there's some kind
of rounding area
Brain fart: that should of course be "rounding error".
that is making part of the surface be "real" and infinitesimally thin.
The usual trick is, when you difference or intersect objects, to
ensure that the objects protrude a bit so that they don't do that, so
that the surface is cleanly removed or not-removed, e.g.:
difference() {
cube(10, center=true);
cylinder(d=5, h=10.1, center=true);
}
Here's a quick change that will make the effect go away in your model:
module port(d){
hull() {
fudge = d ? 0 : 0.1;
cube([19.5+d*2,15+d*2,2 + fudge],center=true);
translate([-10,4,15])
rotate([0,-60,0])
cube([7+d*2,14+d*2,2 + fudge],center=true);
}
}
Note that you have the same issue on the bottom too, which is why I
put in the fudge factor there too.
That 0.1 difference slightly changes the geometry of the model. If
that's important to you then you might need something more complex.