Hello There Animation by Jordan Brown

/*
 This script was presented by Jordan Brown in the OpenSCAD
 forum to illustrate how an object could be used to control
 an animation

 Demonstration animation.
 The animation was built to run with animation parameters
 set to FPS=10 and steps=100.
 */

v = version();
//echo( _v.x, _v.y, _v.z );
assert( _v.x== 2025 && _v.y>=7 && _v.z >= 11 );

//Remember that this requires 2025.07.11. Zoom as desired.

// Best view is looking straight down at the origin.
$vpr = [0,0,0];
$vpt = [0,0,0];

/*
 This vector is a description of everything that happens
 during the animation. You want a wide window to read it.
 The only thing that's defined is "t", the timestamp for that
 particular entry. The rest are up to your program.
 For this animation:
  pos1, pos2: the {red, green} stick man's position
  arm1, arm2: the {red, green} stick man's arm angle
  says1, says2: what the {red, green} stick man is saying
 */
timeline = [
object(t=0, pos1=[-50,0,0],
              arm1=-30, says1="",
              pos2=[50,0],  arm2=-30, says2=""),
object(t=2.5, arm1=-30 ),
object(t=3,   arm1=50,  says1="Hey, George!"  ),
object(t=3.5, arm1=-30 ),
object(t=5,             says1="" ),
object(t=5.5,               arm2=-30 ),
object(t=6,                 arm2=50, says2="Hey, Fred!" ),
object(t=6.5,               arm2=-30 ),
object(t=7,                     says2="" ),
object(t=12, pos1=[-5,0,0],  pos2=[5,0] ),
object(t=13,            says1="Can I go past?" ),
object(t=14,            says1="" ),
object(t=15,                    says2="Sorry, no." ),
object(t=16,                    says2="" ),
object(t=17,            says1="I hate living on a number line!" ),
object(t=19,            says1="" ),
object(t=19.5,                  says2="Me too!"  ),
object(t=20.5,                  says2="" ),
object(t=22, pos1=[-5,0,0],
                            arm2=-30,
                        says1="", pos2=[5,0],
                            arm2=-30,
                                says2="" ),
];

// Now, create the current frame of the animation.

// Get the current values of all of the timeline columns.
a = animate(timeline);
/* Using those values,
   create the model at this moment.
   There are two stick men.
 */
translate(a.pos1) {
    color("red")
        stickman(a.says1, a.arm1);
    }
translate(a.pos2) {
    color("green")
        stickman(a.says2, a.arm2);
    }

// Create a stick man, holding his arms at the specified angle and saying what's specified.
module stickman(says, arm) {
    square([1,8], center=true);
    translate([0,5])
        circle(2);
    translate([0,2])
        rotate(arm)
            translate([0,-0.5])
                square([4,1]);
    translate([0,2])
        rotate(180-arm)
            translate([0,-0.5])
                square([4,1]);
    translate([0,-4])
        rotate(200)
            translate([-0.5,0])
                square([1,5]);
    translate([0,-4])
        rotate(160)
            translate([-0.5,0])
                square([1,5]);
    translate([0, 8])
        text(says, halign="center", valign="baseline", size=3);
    }

// The rest is generic support for using a timeline like that.

// Extract one column from an animation timeline, extracting only
// those entries where that column is present.
function animate_extract(list, key) = [
    for (e = list)
        if( !is_undef(e[key]) ) [ e.t, e[key] ]
    ];

// Get the duration of the timeline, the timestamp of the
// last entry in the timeline.
function animate_duration(list) = list[len(list)-1].t;

// Given $t, a timeline and a key, interpolate the current value
// of the key.
function animate_interpolate(list, key) =
    xlookup(
        $t * animate_duration(list),
        animate_extract(list, key)
        );

// Get a list of all keys used in the timeline.
function animate_keys(list) =
    let( o = object(
            [
            for (e = list)
                for (k = e) [ k, true ]
            ]
            )
        )
    [ for (k = o) k ];

// Given $t and a timeline, return an aggregated object with the
// current values of all of the columns of the timeline.
function animate(timeline) =
    let(keys = animate_keys(timeline))
    object(
        [
        for (k = keys)
            [ k, animate_interpolate(timeline, k) ]
        ]
        );

// lookup() on steroids. Given a value and a lookup-like list,
// do the lookup and interpolation that lookup() does... but have
// it also work for strings, booleans, and identical-length lists
// of numbers.
function xlookup(val, list) =
    is_num(list[0][1])      ? lookup(val, list)
    : is_string(list[0][1]) ? lookup_string(val, list)
    : is_bool(list[0][1])   ? lookup_bool(  val, list)
    : is_list(list[0][1])   ? lookup_list(  val, list)
    : assert(false, "don't know how to lookup that type")
    ;

// Given a value and a lookup list, return the index of the entry
// before (or matching) the value.
function lookup_prev(val, list) =
    let (tmp = [ for (i = [0:1:len(list)-1])
        [ list[i][0], i ] ]
        )
    floor(lookup(val, tmp))
    ;

//Given a value and a lookup list, return the index of the entry
// after (or matching) the value.
function lookup_next(val, list) =
    let (tmp = [ for (i = [0:1:len(list)-1])
        [ list[i][0], i ] ]
        )
    ceil(lookup(val, tmp))
    ;

// Given a value and a lookup list containing strings, return the
// string before (or matching) the value.
function lookup_string(val, list) =
    list[lookup_prev(val, list)][1]
    ;

// Given a value and a lookup list containing booleans, return the
// boolean before (or matching) the value.
function lookup_bool(val, list) =
    list[lookup_prev(val, list)][1]
    ;

// Given a value and a lookup list containing same-length lists of
// numbers, interpolate values for the list. Note that because
// lookup_prev() and lookup_next() return the same entry on an exact
// match, and that leads to 0*0/0, that case has to be handled
// specially.
function lookup_list(val, list) =
    let(
        p = lookup_prev(val, list),
        n = lookup_next(val, list)
        )
    p == n ?
        list[p][1]
    :   list[p][1] +
            (list[n][1]-list[p][1]) *
            (val - list[p][0]) / (list[n][0] - list[p][0])
    ;