Falling Null attached to another null so it swings

[Graham Quince]

I feel like I’m really close with this, but I’m stuck. I’m trying to have one Null parented to another, but have it fall due to gravity. I want this constrained so that when it hits the maximum length it starts to swing under.

I thought clamp() would help, but I can’t see how to manage the X position.

g = 10; // gravitational constant
y = g*time*time/2;
xPos = value[0];
yPos = clamp(y,0,250);
[xPos,yPos];

Any ideas?

[Graham Quince]

I’m getting closer, I realised I can use @danebberts bounce expression to describe the x movement swinging in:

g = 10; // gravitational constant
y = g*time*time/2;
xPos = value[0];
yPos = clamp(y,0,250);
if (yPos == 250) {
    t = time - inPoint;
    startVal = xPos;
    endVal = 0;
    dur = 0.1;
    xPos = linear(t,0,dur,startVal,endVal);
}
[xPos,yPos];

I just have to figure out how to set t to not be based on the inPoint, but the moment when Y crosses the 250 threshold.

[Graham Quince]

I’m getting closer, but it’s still the time that’s the issue, I need to replace the inPoint value with the timestamp from when y is clamped.

xPosStart = 1200;
yPosStart = 540;
parentPos = thisComp.layer("Null 1").transform.position;
gravity = 10;
distance = length(transform.position,thisComp.layer("Null 1").transform.position);
rope_length = 400;
if (distance >= rope_length){ // once the null is at the max length of the rope, kick in Dan Ebberts's overshoot expression
	t = time - xStartTime;
	freq = 3;
	decay = 5;
	startVal = [xPosStart,y];
	endVal = [parentPos[0],parentPos[1]-rope_length/2];
	dur = 0.1;
    if (t < dur){
        linear(t,0,dur,startVal,endVal);
    } else {
        amp = (endVal - startVal)/dur;
        w = freq*Math.PI*2;
        endVal + amp*(Math.sin((t-dur)*w)/Math.exp(decay*(t-dur))/w);
    }
} else { // Fall straight down, until at end of rope
	xStartTime = time;
	yPos = gravity*100*time*time;
	y = clamp(yPos,yPosStart,yPosStart+rope_length);
	[xPosStart,y];
}

It’s not giving me an error, but it’s stopping