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M
MrG2EK
Participating Frequently
January 1, 2023
Answered

modifying value at a specific keyframe with an expression

  • January 1, 2023
  • 2 replies
  • 1083 views

Hey everyone 🙂 i could use some help with some expressions 
I'm currently working on animated background, (scrolling logo)
I'm trying to find a way to create some controls for the directions of the animation.
To do that i need to be able to modify the value of either the 2nd keyframe or a specific timestamp(0;00;29;29).
My idea so far was to created 2 scroll down menus (one for X axis one for Y).
and i tried to find an expression that would look like this : 
I'm really new at this so all help would be appreciated

M1 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION HORIZONTAL")("Menu");
M2 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION VERTICAL")("Menu");
P = key(2)

if (M1==1)(P=(8000,[1]))
if (M1==2)(P=(0,[1]))
if (M1==3)(P=(-8000,[1]))
if (M2==1)(P=([0],8000))
if (M2==2)(P=([0],0))
if (M2==3)(P=([0],-8000))


so far i haven't found anything that worked, so i'd really appreciate some help with this. 
Let me know if i wasn't clear or if you need more informations. 
Thank you. 

This topic has been closed for replies.
Correct answer Dan Ebberts

As Mylenium has pointed out, an expression can't just affect the value at a particular keyframe. Once you apply an expression, it calculates the value at every frame (although that calcualation can include the keyframed value). I think you were close to achieving what you're after, and something like this should work:

M1 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION HORIZONTAL")("Menu");
M2 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION VERTICAL")("Menu");
T1 = key(1).time;
T2 = key(2).time;
V1 = key(1).value;

if (M1 == 1)
  X = 8000
else if (M1 == 2)
  X = 0
else
  X = -8000;

if (M2 == 1)
  Y = 8000
else if (M2 == 2)
  Y = 0
else
  Y = -8000;

V2 = [X,Y];
linear(time,T1,T2,V1,V2)

2 replies

Mylenium
Mylenium
Legend
January 2, 2023

You misunderstand how the process works. You cannot manipulate the keyframe's actual stored value, you override it with your expression and somehow it still needs to interpolate with the previous/ next keyframes. The snippet I provided applies regardless whether it's a native position control or an effect control like in Motion Tile. Having the values as pairs inside two separate dropdowns just doesn't make a lot of sense. Sure, there would be ways to combine them, but why would you create a lot of extra code to fix something that can be cured more easily? Anyway, beyond what I provided it's really not clear what you actually want to do. You really have to explain better what this is all about and provide a screenshot.

 

Mylenium

    M
    MrG2EKAuthor
    Participating Frequently
    January 2, 2023

    Alright so i'm working on looping backgrounds, so far i created 6 of them :

    they pretty much all follows the same animation :

    keyframe 1 at 0;00;00;00 :
    Tile center 0,0.0,0

    keyframe 2 at 0;00;29;29 :
    -8000.0,8000.0
    i created an adjustment layer (BG_GUIDE) that i'm using to control my backgrounds 

    i created two dropdown menu ('ANIMATION HORIZONTAL' & 'ANIMATION VERTICAL')
    with 3 Options
    ANIMATION HORIZONTAL : 1 = LEFT (-8000) ; 2 = CENTER (0) ; 3 = RIGHT (8000)
    ANIMATION VERTICAL : 1 = TOP (-8000) ; 2 = CENTER (0) ; 3 = BOTTOM (8000)

    Since motion tile center is given in 2 value [x,y], what i tried to do is use 1 menu for 1 value and 1 menu for the other 
    (i did this this way because i learned how to use expressions through a few tutorials so my knowledge is super limited) 
    what i have no idea how to do is limit this to the second keyframe and not the entire composition. 
    I hope this helps and also i wanted to thank you again for taking the time to help me, i really appreciate it :). 

    Dan Ebberts
    Community Expert
    Dan EbbertsCommunity ExpertCorrect answer
    Community Expert
    January 2, 2023

    As Mylenium has pointed out, an expression can't just affect the value at a particular keyframe. Once you apply an expression, it calculates the value at every frame (although that calcualation can include the keyframed value). I think you were close to achieving what you're after, and something like this should work:

    M1 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION HORIZONTAL")("Menu");
M2 = comp("Comp 1").layer("BG_GUIDE").effect("ANIMATION VERTICAL")("Menu");
T1 = key(1).time;
T2 = key(2).time;
V1 = key(1).value;

if (M1 == 1)
  X = 8000
else if (M1 == 2)
  X = 0
else
  X = -8000;

if (M2 == 1)
  Y = 8000
else if (M2 == 2)
  Y = 0
else
  Y = -8000;

V2 = [X,Y];
linear(time,T1,T2,V1,V2)
    Mylenium
    Mylenium
    Legend
    January 1, 2023

    Your menu's won't do anything because they simply override each other nor do you have actual else{} statements in your ifs, making this a case "Dear user, I'll simply use whatever value I'll find. Sincerely, your expression". Also typing out the position values as pairs makes no sense and only complicates matters. This will simply never work and of course there isn't any actual logic there that handles your keyframes. So all this considered, you need something completely different. I'm only typing out the basic skeleton, but I hope you get the idea:

     

    mLay=comp("Comp 1").layer("BG Guide");
mM1=mLay.effect("Animation horizontal")(1);
mM2=mLay.effect("Animation vertical")(1);

if(M1 == 1)
{mX=8000;}
else if (M1== 2)
{mX=0;}
else
{mX=-8000;}

if(M2 == 1)
{mY=8000;}
else if (M2== 2)
{mY=0;}
else
{mY=-8000;}

mPos=key(2).value;
mTime=key(2).time;
mMove=5; //motion duration in seconds

X=linear(time,mTime,mTime+mMove,mPos[0],mPos[0]+mX);
Y=linear(time,mTime,mTime+mMove,mPos[1],mPos[1]+mY);

[X,Y]

     

    Mylenium

    M
    MrG2EKAuthor
    Participating Frequently
    January 1, 2023

    <<Also typing out the position values as pairs makes no sense and only complicates matters.>>
    Is there a way to separate the dimensions of a tile center ? 

    M
    MrG2EKAuthor
    Participating Frequently
    January 1, 2023

    also thank you for your reply, 
    but no i don't get the idea, like i said before, i'm new to expressions ^^

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