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# Drawing sin wave from the middle

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 Drawing sin wave from the middle by Michaelon Mar 22, 2019 at 12:53:50 am

Hi,

Maybe someone can help me with my problem.
I try to create this sin wave animation, but I cannot figure out how.

https://dribbble.com/shots/3581505-CypherAudio-03

I tried it with this tutorial,

,

but the ball starts with the wave at the left side and moves out on the right side of the screen.
(Of course, depends on the size of your comp, the lengh, the amp and freq..). I want to create a ball drawing sin wave,
where the ball (or circle) stays in the middle of the comp. So the ball only goes up and down and draws a line which goes to the left (or right like in the example.
How do I achieve this? Thanks in advance.
Best
Michael

 Re: Drawing sin wave from the middleon Mar 22, 2019 at 7:21:40 pm

I think this should work for you
Follow that tutorial to make the sine wave.

Now make a rectangle that half the size of your comp on the layer above the sine wave.

Set the sine wave to alpha matte of that top layer. Precomp those two layers together and now you have half a sine wave.

Duplicate the precomp, right click the duplicate and go to transform>flip horizontal.

You should see pretty much the end result at this point, both sine waves should be originating from the center so now just make the ball and animate to cover where the sine waves touch.

 Re: Drawing sin wave from the middleon Mar 22, 2019 at 8:29:51 pm

Actually sorry i didnt realize i stumbled into the expression forum haha. Im not sure how to write an xpression that would do that sorry.

 Re: Drawing sin wave from the middleby Michaelon Mar 23, 2019 at 4:13:07 pm

Hi Max,

thx for your input. The matte solution sounds like a good idea. I used keyframes to re-position the precomp.
Not nice, but it does it job. ðŸ˜‰

best
Michael