Is there a expression which can : value + previous value

[Paul Roper]

Having variables accumulate over time in After Effects is a real pain, but Dan’s your man for this kinda thing; this will hopefully help you a lot:

https://www.motionscript.com/design-guide/audio-count.html

– Paul

[Paul Roper]

…If you want to use Dan’s expression to control a 2-dimensional array (eg. 2D position), just change the last line ( n ) to this, where the *20 is to amplify the amount of movement – change it to suit your needs.

[n*20,value[1]]

[Immanuel Morales]

try using .valueAtTime([time]-[seconds]) and .frameDuration*[number of frames].

var prev = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider").valueAtTime(time-thisComp.frameDuration*2);

[Kurisuta Vd wilk]

i cannot check it right now, but this sounds as a reasonable solution !!

No knowledge is a Statement

[Juan Irache]

I was recently facing a similar problem, where I needed to do some calculation in every frame and add it to a total from the previous frame. The problem with looping through every frame to the current one in every frame is the render becomes increasingly painful for the machine in every frame.

My solution was to make all the calculations on a text layer, in the first frame: I loop through all the frames, push the value of every frame to an array, and print the array as the Source Text. Someting like this:

mSource = thisComp.layer("source layer");
if (time == mSource.inPoint) {
totalValue = 0
values = [0];

for (i=timeToFrames(mSource.inPoint); i

Then, wherever the value has to appear, I pick the text from the first frame, split it by comma to create an array and pick the index corresponding to the frame I'm at:

mSource = thisComp.layer("source layer");
arr = thisComp.layer("text layer").text.sourceText.valueAtTime(mSource.inPoint);
mIndex = timeToFrames(time - mSource.inPoint);
val = arr.split(',')[mIndex];
val

The difference in rendering speed is night and day.

[Sacha Crispin]

Hi Kurisuta! I’ve been trying to understand your explanation for 3 days now but can’t make it work. Would you mind sharing a project file or giving ampler explanation please? Thank you!

[Dan Ebberts]

This might be helpful (the section on time remapping):

http://www.motionscript.com/articles/speed-control.html#other-applications

[Sacha Crispin]

Oh wow thank you so much Dan! Will browse your blog even more now when I’m looking for help from now on. Thank you so much. ❤