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set initial x, y, and z with expression – subsequent frames hold frame 1 values
It seems afx re-runs expressions every frame without remembering previous frame’s variables values. How do you work around this?
I would like to re-use the initial variables (x, y and z) set at frame 1, so that the position is not changing in subsequent frames. Code below.
[code]
if(time == 0){
x = Math.floor(random(thisComp.width));
y = Math.floor(random(thisComp.height));
z = Math.floor(random(-300, 300));
[x,y,z];
} else{
// of course this produces errors
[x,y,z];
}
[/code]I’ve seen similar problems in other posts here, but can’t seem to work those into this scenario. If so, could you please send link?
Thanks -
5 Replies
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Expressions execute at each frame and there is no way to pass data from one frame to the next. The work-arounds depend on what it is that you’re trying to do.
If all you want to do is generate a static random position, you could do it this way:
seedRandom(index,true);
x = Math.floor(random(thisComp.width));
y = Math.floor(random(thisComp.height));
z = Math.floor(random(-300, 300));
[x,y,z];Dan
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Hi Dan,
Thanks for the reply and the code!
Guess you’ve said this a million times by now. I noticed in other forums you’ve answered this same question. Thanks for your patience!
For some reason the code below causes the layer text to disappear after frame 1. Am I missing another step in using this correctly?
Comp set up – 640×480 10 secondsseedRandom(index,true);
x = Math.floor(random(thisComp.width));
y = Math.floor(random(thisComp.height));
z = Math.floor(random(-300, 300));
[x,y,z]; -
I can’t repro the problem here. You have a text layer and you’ve applied the expression to the layer’s Position property, is that correct?
Dan
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Dan, thank you so much! I had another expression that was removing the text value. Works like a charm!
I guess I would like to understand more about wha the seedRandom() method does. Is there any information on this anywhere? The help files are pretty sparse.
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[David Ford] “I guess I would like to understand more about wha the seedRandom() method does. Is there any information on this anywhere? The help files are pretty sparse.”
seedRandom() assigns a continuous – erm – seed to random functions. Randomness in computers is not really random, it’s based on formulas. For instance a common method is Perlin Noise which itself is just a set of overlapping sinus/ cosinus functions with random phase and periods. If you calculate a time dependent sinus with Math.sin(time), your result is a wave. Multiple such overlapping functions with different multipliers (e.g. time*2) create pseudo-random peaks and grooves. By fixing the seed in random functions, you more or less freeze time – with the same input, the result is always the same.
Mylenium
[Pour Myl
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