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Not understanding an expression
Hey all I am reading through the expressions reference in adobe and don’t quite get this part in wiggle:
“Example: position.wiggle(5, 20, 3, .5) produces about 5 wiggles per second with an average size of about 20 pixels. In addition to the main wiggle, two more levels of detailed wiggles occur with a frequency of 10 and 20 wiggles per second, and sizes of 10 and 5 pixels, respectively.”
I understand that 5 is the frequency, 20 is the amplitude, 3 is the octave and .5 is the amp_mult. What I am not understanding is this part:
“In addition to the main wiggle, two more levels of detailed wiggles occur with a frequency of 10 and 20 wiggles per second, and sizes of 10 and 5 pixels, respectively.”
Here is the entire excerpt from the page:
“wiggle(freq, amp, octaves=1, amp_mult=.5, t=time)
Return type: Number or Array.
Argument type: freq, amp, octaves, amp_mult, and t are Numbers.
Randomly shakes (wiggles) the value of the property.
freq value is the frequency in wiggles per second.
amp value is the amplitude in units of the property to which it is applied.
octaves is the number of octaves of noise to add together. This value controls how much detail is in the wiggle. Make this value higher than the default of 1 to include higher frequencies or lower to include amplitude harmonics in the wiggle.
amp_mult is the amount that amp is multiplied by for each octave. This value controls how fast the harmonics drop off. The default is 0.5; make it closer to 1 to have the harmonics added at the same amplitude as the base frequency, or closer to 0 to add in less detail.
t is the base start time. This value defaults to the current time. Use this parameter if you want the output to be a wiggle of the property value sampled at a different time.
Example: position.wiggle(5, 20, 3, .5) produces about 5 wiggles per second with an average size of about 20 pixels. In addition to the main wiggle, two more levels of detailed wiggles occur with a frequency of 10 and 20 wiggles per second, and sizes of 10 and 5 pixels, respectively.
This example, on a two-dimensional property such as Scale, wiggles both dimensions by the same amount:
v = wiggle(5, 10); [v[0], v[0]]
This example, on a two-dimensional property, wiggles only along the y axis:
freq = 3; amp = 50; w = wiggle(freq,amp); [value[0],w[1]];”
If someone could explain it, it would be great.
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4 Replies
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It means that there are three octaves (each octave being a doubling of the frequency) to the noise which get added together, each with half the amplitude of the previous octave. So it would be essentially the same as doing this:
wiggle(5,20) + wiggle(10,10) + wiggle(20,5)
It helps to watch the graph editor as you add each successive octave. It makes the wave more complex, like adding harmonics to an audio waveform.
Dan
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Than you for the reply Dan. Just one more thing. So basically when the frequency multiplies, the amplitude goes down. Is this the case always?
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No, that’s controlled by the 4th (amplitude multiplier) parameter. For example, this would give all the octaves equal weighting:
wiggle(5,20,3,1);
and this would double the impact of each successive octave:
wiggle(5,20,3,2);
Dan
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Thanks for the clear explanation Dan. I was reading through Looping wiggle on your website when I got a response here on Creative Cow haha.
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