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Swinging down and decaying to a stop
startFrame = 14 if (time >= framesToTime(startFrame)){ freq =1.0; amplitude = 50 decay = 1.5; amplitude*Math.sin(freq*2*Math.PI)/Math.exp(decay) }else{ value}Hello all,
I have the basic mechanics for a rotation decay set up, but I need the starting position of the decay to be different from the end position.
Imagine a pendulum that’s sticking straight out to the left, perpendicular to the ground. I need the pendulum to swing down and decay to a stop, with the pendulum resting, pointing to the ground. I’m trying to knock a windmill off it’s tower and I want the blades to swing down and decay before it drops off. It’s starting rotation is zero, but the blades element points left perpendicular to the ground, so in that respect, the actual starting rotation of the element isn’t exactly like a pendulum, but would have the same effect.
The expression I’m using gets the decay right, but it jumps from 0 degrees to about 10.5 before decaying and I have no idea how to get it to swing from the starting point I want.
Thanks in advance for your help.
-Graham
OSX 10.4.11
AE CS3 and 7.0
FC Studio 2.03
Dual 2.7GB PPC G5, 8 GB RAM -
2 Replies
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It’s probably going to look like this:
startFrame = 14
if (time >= framesToTime(startFrame)){
t = time – framesToTime(startFrame);
freq =1.0;
amplitude = 90
decay = 1.5;
amplitude*Math.cos(t*freq*2*Math.PI)/Math.exp(t*decay)
}else{
value
}Dan
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Nailed it.
I did need to subtract 90 from “amplitude*Math.cos(t*freq*2*Math.PI)/Math.exp(t*decay)” to get the element oriented correctly, but otherwise, spot on.
Many thanks.
-Graham
OSX 10.4.11
AE CS3 and 7.0
FC Studio 2.03
Dual 2.7GB PPC G5, 8 GB RAM
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