But only in one direction (down). I could do a hull of said object and a
linear extrusion of its projection onto the xy plane, but it would result
in unwanted space above the object (concave areas) being filled.
Thoughts?
There are possibly simpler and better way to do it but here you have a
starting point:
epsilon = 0.01;
// a test object
translate([30,0,0]) obj();
// its downward extension
extendown() translate([-10,0,0]) obj();
module extendown()
intersection() {
minkowski() {
children();
mirror([0,0,1])
pillar() children();
}
// cylindrical envelope of children
minkowski(){
linear_extrude(height=epsilon)
projection() children();
pillar() children();
}
}
module obj()
translate([0,0,5])
rotate([30,40,0])
{ cube(10);
translate([10,10,0]) cylinder(10,10);
translate([15,0,15]) cube(3);}
// a thin pillar on the origin with height equal to
// the highest point of children
module pillar()
translate([-epsilon/2,-epsilon/2,0])
rotate([-90,0,0])
linear_extrude(height=epsilon)
projection() rotate([0,90,0])
linear_extrude(height=epsilon)
intersection() {
hull()
projection() rotate([90,0,0])
children();
// discard portions of children with negative z
mirror([0,1,0]) translate([-1/epsilon/epsilon/2,0,0])
square(1/epsilon/epsilon);
}
raycewest wrote
> But only in one direction (down). I could do a hull of said object and a
> linear extrusion of its projection onto the xy plane, but it would result
> in unwanted space above the object (concave areas) being filled.
> Thoughts?
There are possibly simpler and better way to do it but here you have a
starting point:
> epsilon = 0.01;
>
> // a test object
> translate([30,0,0]) obj();
> // its downward extension
> extendown() translate([-10,0,0]) obj();
>
> module extendown()
> intersection() {
> minkowski() {
> children();
> mirror([0,0,1])
> pillar() children();
> }
> // cylindrical envelope of children
> minkowski(){
> linear_extrude(height=epsilon)
> projection() children();
> pillar() children();
> }
> }
>
> module obj()
> translate([0,0,5])
> rotate([30,40,0])
> { cube(10);
> translate([10,10,0]) cylinder(10,10);
> translate([15,0,15]) cube(3);}
>
> // a thin pillar on the origin with height equal to
> // the highest point of children
> module pillar()
> translate([-epsilon/2,-epsilon/2,0])
> rotate([-90,0,0])
> linear_extrude(height=epsilon)
> projection() rotate([0,90,0])
> linear_extrude(height=epsilon)
> intersection() {
> hull()
> projection() rotate([90,0,0])
> children();
> // discard portions of children with negative z
> mirror([0,1,0]) translate([-1/epsilon/epsilon/2,0,0])
> square(1/epsilon/epsilon);
> }
<http://forum.openscad.org/file/n21756/extendown.png>
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