Can one make a velocity curve for a variable input?

Adobe After Effects Expressions

Can one make a velocity curve for a variable input?

Posted by Miles andy Thatch on March 13, 2015 at 1:01 pm

I have an audio track that is converted into key frames via key frame assist option. The output is mapped to the intensity of a visual effect via this expression linear(input,inputLow,inputHigh,outputLow,outputHigh) .

Now I need to achieve the effect known to me from music as a velocity curve. It’s like an exponential slope, that dictates how hard one has to press on a key in order to reach the highest value. With a concave curve, light key pressure variations don’t make that much difference but pressing harder increases its effectiveness exponentially, but if the curve is convex then the input sensitivity is very high, this any small fluctuation.Will register a significant change, however, the harder you press, the tougher it is to achieve higher values. That’s velocity curve.

https://www.escom.org/proceedings/ICMPC2000/Tue/Image23.gif

So now I need to make a convex curve for my audio key frames that affect the intensity of an effect. Lower values easily affect the visual fx track but the louder the volume gets, the harder it is for it to achieve higher values.

basic idea is that the audio track drives a video effect, most of the time the audio is really quiet so I have to make its quitest parts to be very effective by saying that the audio key frame doesnt have to reach too high to have a significant effect over the visual. however there are a few occasional loud parts that completely max out the visual effect intensity if I map it directly. so I need to tell the audio keyframes, the lower they are the more they affect the visual effect but the higherthey get, it less effect a make on the visual track.

Thank you.

My Computer:
Windows 7 64bit

HP XW8200
Intel Xeon (2 single processors)
4GB DDR3 memory
Nvidia Gforce Gt 220

Miles andy Thatch replied 11 years, 5 months ago 2 Members · 2 Replies
2 Replies

Dan Ebberts
March 13, 2015 at 1:49 pm

Try it this way:

easeOut(input,inputLow,inputHigh,outputLow,outputHigh)

Dan
Miles andy Thatch
March 17, 2015 at 12:21 pm

Thanks Dan, this just might be what I need. Ill try it at home on today once I’m back. Any possible way to control how steep the curve is?

Thanks you.

My Computer:
Windows 7 64bit

HP XW8200
Intel Xeon (2 single processors)
4GB DDR3 memory
Nvidia Gforce Gt 220

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