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What is wrong with my approach, and how does “my” solution actually works?
Hey all,
I needed to make a calendar in Ae, and I needed a loop of numbers going from 1 to 31. I thought I had enough knowledge of expressions to pull this off, but unfortunately I hadn’t.
This was my approach:
I made a new text layer and dropped a slider control on that.
in the source text of the layer, I create this expression:n = effect("Slider Control")("Slider");Math.round(n)
Now I simply made 2 keyframes om the slider from 1 to 31, and used the loopOut(“cycle”) expression to make it loop. I was now able to adjust the speed with the keyframes, and everything worked fine.
But I wanted to add one thing to it, and that took a lot more work than I thought. Basically I wanted to add a zero in front of the numer when the number was smaller than 10. So I thought I could make that with this expression:
n = effect("Slider Control")("Slider");Math.round(n)
if (n < 10){
n = "0" + n;
}else{
n = n;
}But this doesnt works. it doesnt add a 0 in front of the 1 digit numbers, but it also seems to mess up the Math.round expression.
After some googling I found some expressions to make this work:
s = effect("Slider Control")("Slider");
v = Math.round(time*s);
t = (v%31)+1;
padLength = 2;
t = t.toString();
while (t.length < padLength) {
t = "0" + t;
}
The only things I changed was the added slider for the speed (I believe the expression was v = Math.round(time/thiscompduration); of something like that.
It does exactly what I want, but I don’t understand exactly how. also, when I make v the slider value, it also gives me errors.
So my question is: What did do wrong in my approach, and how does the expression that works actually works? I’m really curious what toString actually does, what “(c%31)+1” does and why they used “while” instead of “if/else”
Regards,
Ramon Peppelenbos
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4 Replies
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You were so frustratingly close in your solution.
The only thing wrong was that you didn’t assign the value derived by Math.round(n) to anything. Math.round(n) is a pass by value function not a pass by reference, so you need to assign the result to something.
Also, for brevity, you don’t need the else clause because if n>=10 it won’t be changed by your if clause.
Modified code below.
Hope this helps.
n = effect("Slider Control")("Slider");
n=Math.round(n)
if (n < 10){ n = "0" + n; }Declan Smith
https://www.madpanic.tv
After Effects CS6/ FCS3 / Canon XLH1 / Canon 7D / Reason / Cubase"it's either binary or it's not"
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Thanks a lot! never heard about “pass by value function” or “pass by reference” before, but I kinda get an idea on what it means. I do understand now what I did wrong, and why I should assign Math.round to a variable. Good to hear I was close though!
Regards,
Ramon Peppelenbos
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To answer the second part of your question:
This expression enables you to have a slider value that can be almost any value, i.e. keyframe it from 1 to 200.
v = Math.round(time*s); This makes the value v related to time so you don’t have to set keyframes for your slider value. By multiplying it by time, it will effectively auto increment.t = (v%31)+1;
The % operator is modulo. So this will take whatever value v is, divide it by 31 and give you the remainder. So if v was 64, t would be 3, if v was 31, t would be 0, hence adding 1 will ensure you get 1 – 31 displayed.
t.toString();
As t is an integer, the toString() method returns a string representation of the number, the equivalent of “” + t
I would guess that the while loop is there because this expression was used for some other purpose originally, where perhaps the number range was larger and therefore, a consistent number of padded 0’s was needed. If you increase the padLength to 4, you will see the effect. Your number will be padded with up to 4 0’s.
Declan Smith
https://www.madpanic.tv
After Effects CS6/ FCS3 / Canon XLH1 / Canon 7D / Reason / Cubase“it’s either binary or it’s not”
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Thanks a lot for the additional information!
Regards,
Ramon Peppelenbos
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