OpenSCAD rounding with offset

offset.scad

// Animation showing what the 4x offset rounding trick does.

$fs = 0.1;
$fa = 0.1;

function clamp(x) = min(max(x, 0), 1);
    

module timed_offset(t) {
    a = clamp(t-1);
    b = clamp(t-2.5);
    c = clamp(t-4);
    d = clamp(t-5.5);

    offset(d) offset(-c) offset(-b) offset(a) children();
}


module some_shape() {
    difference() {
        square(10, center=true);
        translate([2, 0]) square([8, 4], center=true);
    }
}

timed_offset($t * 7.5) some_shape();

(You might have to click play on the above to see the animation.)