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Y position oscillates between numbers with holds
What I’ve been fiddling with for the last few days is to have the Y position oscillate between 2 values, and then hold for a random period of time. I’ve tried so many variables of oscillation and fiddling with the time factor, but I’m not smart enough to make this work. It would basically help me to create a line like this (attached) using a simple particle emitter.
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5 Replies
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I’m not sure if this is what you’re after, but it might give you some ideas. Apply the expression to a layer’s position property and look at the result in the graph editor.
minHold = .25;
maxHold = 1.5;
rampTime = .2;
rampAmount = 100;
t = tPrev = 0;
while (t <= time){
seedRandom(t,true);
hold = random(minHold,maxHold);
period = rampTime*2 + hold;
tPrev = t;
t += period
}
deltaT = time - tPrev;
if (deltaT < rampTime)
y = linear(deltaT,0,rampTime,0,rampAmount)
else
y = linear(deltaT,rampTime,2*rampTime,rampAmount,0);
value + [0,y]
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That works perfectly! I can adjust the rampTime to create a more triangle wave look or turn it way down to get a more square wave. Thanks again, Dan! Screenshot shows designer artwork under the animated emitter with your expression added to the emitter’s position property.
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One thing I noticed is the Y position height is constant. Is there a way to randomize the rampValue to achieve a different height each time and maintain the triangle shape? I tried to add a wiggle to the value, but not only does it change the heigh but also the shape.
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Try this:
minHold = .25;
maxHold = 1.5;
rampTime = .2;
rampAmount = 100;
minRampMult = .75;
maxRampMult = 1.25;
t = tPrev = 0;
rt = rampTime;
ra = rampAmount;
while (t <= time){
seedRandom(t,true);
hold = random(minHold,maxHold);
rampMult = random(minRampMult,maxRampMult);
rtPrev = rt;
raPrev = ra;
rt = rampTime*rampMult;
ra = rampAmount*rampMult;
period = rt*2 + hold;
tPrev = t;
t += period
}
deltaT = time - tPrev;
if (deltaT < rtPrev)
y = linear(deltaT,0,rtPrev,0,raPrev)
else
y = linear(deltaT,rtPrev,2*rtPrev,raPrev,0);
value + [0,y]
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It’s perfect!! Thank you Dan
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