Converting y position velocity to scale

[Graham Macfarlane]

What expressions have you tried so far?
I use an older AE so I can’t open your project.

Graham Macfarlane – CGI specialist
Elyarch Ltd – London UK

3D Studio Max | Vray | Pflow | PhoenixFD | After effects | Mocha

[Wick Van den belt]

Hi Graham, I have been trying so many things but over-written all that I’ve used in the process..

I guess the right way would be to either First get the velocity or speed of the Y-position, or an actual increase in Y position and map that to an increase in the value that the expression is added to with a Clamp.

thisComp.layer(“BUG”).transform.yPosition.velocity;
linear(velocity, 0, 10, 0, -10);

I am really new to expressions so I’m really not sure what would be the right one here.
I tried tweaking the squash and stretch expression from motionscript.com but also with a lot of tweaking that didn’t gave me the results I was looking for… I think that some else-if ideas and definitely some easing would really help sell the effect.. and well, in the worst case I end up keyframing it after all :))

Any ideas here would be greatly appreciated!

Cheers,

Wick

WickieMedia.net

[Graham Macfarlane]

I modified a script by Chris Wright which should give you something to work with. Put the script below into the scale of a null. The null must also have Y position keyframes for the jumping. Just pick whip your bug to the null and you should see the effect.
My null started at 540 and rose up to 360 so in lines 2 and 3 you need to adjust the script for your specific null. The 50,0 and -50,0 control the amount of squash/stretch.

Y = transform.position[1];
Yresult = linear(Y, 360, 540, 50, 0);
Xresult = linear(Y, 360, 540, -50, 0);

// Inertial Bounce (moves settle into place after bouncing around a little)
//By Chris Wright
//Modified by Graham Macfarlane

n = 0;
if (position.numKeys > 0){
n = position.nearestKey(time).index;
if (position.key(n).time > time){
n = n-1;
}
}
if (n == 0){
t = 0;
}else{
t = time - position.key(n).time;
}
if (n > 0){
v = position.velocityAtTime(position.key(n).time - thisComp.frameDuration/10);
amp = .02;
freq = 3.0;
decay = 5.0;
s= v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
value + [Xresult+s[1], Yresult-s[1]];

}else{
value;
}

Graham Macfarlane – CGI specialist
Elyarch Ltd – London UK

3D Studio Max | Vray | Pflow | PhoenixFD | After effects | Mocha