If so, I would expect that bbox0() children() in the following version would
be cached but my tests show the opposite. T() as before.

module complexbbx(p)
intersection(){
render() projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
projection() bbox0() children();
}

module bbox0()
linear_extrude()
intersection() {
ext = pow(2,16);
hull() {
translate([ ext,    0]) children();
translate([-ext,    0]) children();
}
hull() {
translate([    0, ext]) children();
translate([    0,-ext]) children();
}
}

projection() bbox0() T();
complexbbx([1,1]) T();

Even if bbox was cached you are calling projection many times and it is the
odd one out as it is a very slow CGAL operation but it produces a 2D
results, so perhaps not cached.

On Fri, 1 Nov 2019 at 20:10, Ronaldo Persiano rcmpersiano@gmail.com wrote:

I checked that the projection of a cube (like bbox0() is) and  the
intersections have a negligible runtime in this case. The repetitive
computation of bbox0() children() (a 3D object) is what is slowing the run.

A simpler and more dramatic case is the following:

module complexbbx3(p)
projection()
intersection(){
render() children();
children();
children();
children();
children();
children();
children();
children();
children();
}

module bbox0()
linear_extrude()
intersection() {
ext = pow(2,16);
hull() {
translate([ ext,    0]) children();
translate([-ext,    0]) children();
}
hull() {
translate([    0, ext]) children();
translate([    0,-ext]) children();
}
}

complexbbx3([1,1])  bbox0() T();

Here, bbox0() T() is a 3D solid, a cube.  complexbbx3(p) applied on a cube
do just the intersection of 9 equal cubes and project it into a square. The
intersection of 9 equal cubes and the (only one) projection have negligible
runtime compared with the bbox0() operation. What the runtimes show is that
the children of  complexbbx3() are evaluated 9 times. So, its children
geometry (a 3D solid) is not cached.

What happens if you put render() linear_extrude() in bbox()?

On Fri, 1 Nov 2019 at 20:49, Ronaldo Persiano rcmpersiano@gmail.com wrote:

Sorry but my last tests were wrong. It seems that the geometry of bbox0()
T() is really cached. That is, it seems that only 3D geometry are cached,
what is a shame.