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somebody analyses this expression into simple math language
This is a bounce-motion expression
Can really anyone explain this expression? It’s not really hard for me to understand the expression but I want to know its mathematical relations and analysis.
THANKSvar bouncesPerSecond = 1.5;
var bounceStrength = 200;
var decayRate = .5;
var floor = thisComp.layer( " floor " ).transform.
position[1];
var bounceOffset = Math.abs(Math.cos(bouncesPerSecond
* time * 2 * Math.PI));
var y = bounceStrength * bounceOffset/Math.exp(decay
Rate * time);
floor = floor = (height/2);
[position[0], floor] = [0,y] -
1 Reply
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That expression has some errors, but basically, it’s using an exponentially damped, full-wave rectified cosine wave to define a bounce path. This expression does the same thing (I think) and might be slightly easier to understand. Just position your layer above the layer named “floor” and it will drop from there and bounce:
freq = 1.5;
decay = .5;
floor = thisComp.layer("floor").transform. position[1];
d = value[1] - floor;
y = d*Math.abs(Math.cos(freq*time*2* Math.PI))/Math.exp(decay*time);
[value[0],floor] + [0,y]
This kind of expression works pretty good for an oscillating motion (like a spring or pendulum) but isn’t very realistic as a bounce, because when something bounces, the frequency increases as the bounce height gets smaller. That makes it a much trickier expression though.
Dan
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