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Pendulum waves
Hi all.
I stumbled this video: https://www.youtube.com/watch?v=yVkdfJ9PkRQ
i was trying to recreate something like that using expressions.In brief: i need to have a series of pendulums swinging at a given frequncy (f) (let’s say 15 pendulums swinging each at a frequency from 51 to 65 oscillations per minute), and I need that the lenght of every pendulum’s arm depends on the frequency.
I’m not that good with expressions or with physics, so that is what I came out with, incomplete and not working:
I create a round shape with a masked solid, let’s say 60 pixels wide, and i wrote the following expressions for rotation and anchor point:Do my expressions make any sense?
How would you make it?
thanks.Alessandro
anchor point:f= effect("oscillations per minute")("Slider")/60;
T= 1/f;
g= effect("gravity")("Slider");
L= (T*T*g)/((4*Math.PI)*(4*Math.PI));anchorPoint[0],(anchorPoint[1]-L)]
rotation:
f= effect("oscillations per minute")("Slider");
T= 1/f;
g= effect("gravity")("Slider");
L= (T*T*g)/(4*(Math.PI*Math.PI));
maxAmp=effect("maxAmp")("Slider");Math.cos((time/T))*maxAmp
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3 Replies
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I think I’d leave gravity out of it. I used small circles (20×20 solids), and this seems to work:
// anchor Point
shortLen = 100;
longLen = 300;
numPendulums = 15;myLen = linear(index,1,numPendulums,shortLen,longLen);
value – [0,myLen]// rotation
shortLen = 100;
longLen = 300;
numPendulums = 15;freq = .2; // frequencey of longest pendulum
amp = 80;myLen = linear(index,1,numPendulums,shortLen,longLen);
myFreq = (longLen/myLen)*freq;
amp*Math.cos(myFreq*time*Math.PI*2)Of course, you could tie any/all of the parameters to sliders. The expressions assume that the pendulums are at the top of the layer stack.
Dan
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Oops, I forgot about the square root relationship between the length and the period. The rotation expression should probably be more like this:
// rotation
shortLen = 100;
longLen = 300;
numPendulums = 15;freq = .2; // frequencey of longest pendulum
amp = 80;myLen = linear(index,1,numPendulums,shortLen,longLen);
myFreq = Math.sqrt(longLen/myLen)*freq;
amp*Math.cos(myFreq*time*Math.PI*2)Dan
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brilliant.
Thank you so much.
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