How To Animate Accurate Physics With Expressions – After Effects Tutorial


hiya James we’re from here for plugging
everything and so we’re gonna be talking about how we can animate physics by
expressions if you’re anything like me I can’t animate for peanuts and so
expressions really help me with that especially physical based expressions
such as balance elastic etc so in this example I’ve just got a ball that drops
and it’s got its default linear ease which is boring so I just select those
and apply the bounce expression for ease and whizz this is a NAME YOUR OWN PRICE script from aescripts.com with the original expressions I believe based on Penner’s
easing expressions which you can find more about here at Robert panakam slash
easing so we simply select keyframe apply bounce out and been there we go
we’ve got our ball bouncing the great thing about this is that just so we
wanted to drop the ball from a little bit higher we can simply increase the
height of the drop and it updates automatically which is great very easy
to iterate so that was very easy let’s try a more complex example we’re going
to animate some shapes using elastic instead of bounce I’m just gonna create
a new solid and add an ellipse to that and just scale it down to 90% then
change its opacity to very low this is just a guide for me because I want to
draw essentially a bit of rope that’s been stretched all the way back so two
points and then vertex in the middle we drag that all the way down and I’m gonna
draw this at its starting point where it’s been stretched back as far as it
can go and the reason I had the circle is because I want it to emulate the look
of a circle at this stage so we go content shape path keyframe that then
I’m gonna come to four seconds and this path here I want it to essentially be at
its resting state at the start it’s been stretched and then once it’s stopped
wobbling comes back to this resting state issue I currently have is that the
handles are too long at the end and so all the animation looks good at the
start at the end these handles shouldn’t be as long so if we just come to the
second keyframe we can just make these shorter and then we’ll get a more
natural-looking animation towards the end we want to use the elastic
expression which overshoots the end of your animation and shows a bit more
so what we need to do is then come to say eight seconds and draw our overshoot
animation which is very easy it’s essentially the same as the first
keyframe but just all the way at the other end rather that’s kind of what we
would expect if you slung a slingshot and then it went all the way up here and
then it would come back to its resting place so I’m pretty happy with this
animation if we were to apply say Expo in and out or expert out to this it
would say looks like you have a mask path selected so to apply is in ways you
need to use the curvaceous checkbox that’s because instead of just numbers
were actually interpolating between paths and that’s going to work that’s
now applied the expert out however curvaceous doesn’t work for
elastic or back and that’s because it has that overshoot and it doesn’t know
that you if you’ve supplied it or not we have supplied it here there overshoot
but it doesn’t know that so we need to cheat this a little bit we need to grab
comp one actually before I do that I just click that and remove that
expression I just want the linear ease drag comp on into a new comp go time
time remapping then come to our resting point set a keyframe delete the last
keyframe and now we don’t need this curvaceous because now we are dealing
with number data here instead of paths and we go move a curvaceous get elastic
out now if we play that back it’s not going to look very good and the reason
for that is if we actually display this if we visualize what’s going on here we
can see it’s too extreme the amplitude is way too high so to set this up I’m
just going to add two sliders the first one’s gonna be period and the second
one’s going to be amplitude and then if we go into the expression itself you can
see we’ve got the period here which is point eight one I believe that’s usually
a value between zero and one and that’s the time distance between the keyframes
and the amplitude is how far it’s going to shoot so if we have these both set to
zero I don’t know what’s going to happen actually okay it’s just the default
animation make the period like two point eight one and we can again visualize
these but the amplitude is still zero let’s
that up to say two so there we have our wobbling animation it’s a little bit
boring though so we might want to increase the amplitude and if we go too
high we’ll see we get this clipping where it’s gone past eight seconds
remember we don’t have any animation past eight seconds so that’s it’s just
gonna be blank there so we can’t go too high but you can if you want you just
got to make sure you’ve got the overshoot animation for it to display I
don’t want it to be that high I’m going to try that your six the great thing
about this is this updates if we make a change we can see that same with the
period but I think the about your point eight one suits it I think this is
looking pretty good but I wanted to sort of shoot out at the start quicker and
what we can do to do that is instead of having this resting point at exactly the
middle we can speed up the start and then have the end slower but now that
we’ve changed the resting spot to be three seconds 15 frames we need to
update that here otherwise the resting spot is going to be you know not halfway
so we just click on this and make this three fifteen so now it’s a bit bounce
here at the start the other thing we want to do is probably turn this into a
guide layer so that we can’t see it also I believe the stroke looks better on
Sena mayshen using a round cap rather than a bite cap that’s looking pretty
good I still think the handles at the resting spot are too long and so it’s
making it look a little weird so I’m just going to shorten those I think that
looks a lot better in the final result that I’ve got I’ve added a plugin that
coincidentally plug-in everything makes called path visualizer to display the
handles and the vertices and then I’ve just animated a very quick pen tool
animation to show that the pen tool is what’s pulling back the elastic and and
loosing it and then I simply just looped it so that it can play forever so make
sure you check out plugging everything comm we’ve got heaps of cool
plugins some of my free most of them aren’t but that’s how it can afford to
sustain ourselves but thanks for watching and I hope you create something
cool with expressions you

4 Comments

  1. Expressions and physics animations…. they sound terrifying to get involved with, but the truth is we can get into these techniques pretty easily. Today James dives into
    in a step by step guide to help you. What other techniques do you want us to cover?

    If you want to see our other work you can click our channel page here (Also, subscribe) — > bit.ly/JoinThePluginParty

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