Custom speeds when easing via expression ease(t,a,b,x,y)

[Dan Ebberts]

You’d have to be able to convert your ease to a formula of some kind. Maybe one of the Penner eases comes close to what you need.

Dan

[Tilman Commes]

Thanks for the reply!
I will look into that!

[Matt Volp]

Hi Tim,

I’d love to know what the solution to this was.

Also, could you explain your workaround in a little more detail; it sounds very interesting!

Cheers.

[Tilman Commes]

I’m sorry Dan, could I ask for your help once more?
I’m not quite sure how such a formula would look like.

Could this formula be built in such a way that you insert the values that you would usually adjust in the Keyframe-Velocity-Menu?

[James Ronan]

This was my approach when doing something similar… Maybe it will help you get started. It doesn’t have custom controls for velocity though.

Add as an expression on the position property of a layer. It will move the layer 500px along the x axis between 1 – 2 seconds.


function easeInOutCubic(t) { return t<.5 ? 4*t*t*t : (t-1)*(2*t-2)*(2*t-2)+1 };

startVal = 0;
endVal = 500;
startDur = 1;
endDur = 2;

t = linear(time,startDur,endDur,0,1);
e = easeInOutCubic(t);
x = linear(e,0,1,startVal,endVal);

[x, value[1]];


I took the easeInOutCubic function from this website which has a variety of easing functions:
https://gist.github.com/gre/1650294

Hope that helps

[Jacob Mellin]

Hi,

I think I have come up with a solution that allows you to use a custom easing function for easing between any two keyframes for a property. I am new to expressions, so there may be some issues, but it worked for me. I tested it on scale and position properties.

EDIT: Sorry, I totally disregarded the fact that the question was about not using keyframes… Maybe someone will find this helpful anyway…

You should be able to simply create two keyframes, as you normally would. After the function definition, call easeSingleProperty with an easing function and the two keyframes you want to tween the values for as arguments. The expression will use the property values and the time of the keyframes.

Use any easing function that takes a value between 0 and 1 and returns an (eased) value between 0 and 1. This gist (and discussion thread) contains some functions that you could use: https://gist.github.com/gre/1650294

You could use https://easings.net/ for reference.

Maybe it helps someone. 🙂

function easeInElastic(t) { return (.04 - .04 / t) * Math.sin(25 * t) + 1 }

function easeSingleProperty(easingFunction, startKey, endKey) {
var startTime = startKey.time
var endTime = endKey.time
if(time > startTime && time < endTime) { var progress = 0; progress = (time-startTime)/(endTime-startTime); var easedProgress = easingFunction(progress); return startKey + (endKey-startKey)*easedProgress; } return value } easeSingleProperty(easeInElastic, key(1), key(2))

[Matthias Stoll]

Hi Tilman, hi everybody

Thanks for the thread and all the ideas! I combined some of the ideas to do it, based on the Penner eases. In this expression you can define start and end values in two dimensions. On top 3 Penner functions are defined, at the bottom you have to pick between EaseIn, EaseOut, EaseInOut.

I hope someone out there still needs this…

EaseIn = function(power){return function(t){return Math.pow(t, power)}};
EaseOut = function(power){return function(t){return 1 - Math.abs(Math.pow(t-1, power))}};
EaseInOut = function(power){return function(t){return t<.5 ? EaseIn(power)(t*2)/2 : EaseOut(power)(t*2 - 1)/2+0.5}}

dur=1; power=5; //1=linear, 2=Quad, 3=Cubic, 4=Quart, 5=Quint
startX=value[0]; startY=value[1];
endX= ; endY= ;

t=linear(time-inPoint,0,dur,0,1);
Exp=EaseOut(power)(t);
x=startX+(endX-startX)*Exp;
y=startY+(endY-startY)*Exp;
[x,y]

[Marc Pelletier]

Hey Matthias,

thanks for the post, very useful stuff!

I just noticed a little typo in you EaseInOut function, or it might be an issue with the HTML characters. I believe it should be written as follows :

EaseInOut = function(power){return function(t){return t < 0.5 ? EaseIn(power)(t*2)/2 : EaseOut(power)(t*2 – 1)/2+0.5}};

Thanks again!

EaseInOut = function(power){return function(t){return t < 0.5 ? EaseIn(power)(t*2)/2 : EaseOut(power)(t*2 - 1)/2+0.5}};

[Obed Ampong]

Thanks a lot.

Regards

Obed

[Owen Rucker]

Is there a way to create an easing function formula based off the Bezier values seen in the FLOW plugin?

eg: [0.40,0.00,0.20,1.00]

Sorry, I don’t know the math.