Hi,
The attached file shows a simple smooth fade (taken from Farnell's"Designing Sound"). He writes: "A good way to obtain a smooth fade is to convert messages to a signal with [sig~] and then low pass filter it with [lop~]. A cuttoff value of 1Hz will make a fade that smoothly adjust over 1 second."

I do not understand what's the logic behind this rule. In the patch, a value (0-1) is transformed into signal, which means 64 samples of the same value, which are sent as a single block into the cold inlet of [*~]. So what's the deal with frequency here? Can someone clarify?
Thanks a lot

http://www.pdpatchrepo.info/hurleur/figure_14.6.tiff

dullard: Yeah, that probably is an easier way to think about it.

Thanks for describing it more succinctly than I could Maelstrom (edit: and dullard)

Thanks for the patch, very interesting to know about [lop~] being log going up and exp going down. It's similar to the curve you get for an rms average.

I was wondering how I could make S-curves, I'll have to check out Bessel filters (currently using vanilla though).

I was doing crossfading a few weeks ago and found using the cos~ function to create equal power curves pretty useful.

@ymotion said:

Jwif - the Xn are the values coming from the slider, and Yn are the frequency after a lop was applied?

Almost. Like you said, the Xn graph represents the slider going from 1 to 0 very quickly.

Yn is not showing the frequency but rather the change in sample values (from 1 to 0) over a longer period, this is the output of the [lop~]. How fast this occurs would be the frequency.

OK, It is complicated, but I think I got it now.
Maelstorm & dullard: thanks for the visual descriptions. It's easier for me to follow this way...

@Maelstorm said:

I fairly recently was trying to make one of those smoothed-out sample-and-hold LFOs and discovered that [lop~] generates asymmetric curves: logarithmic going up and exponential going down.

Well, it's actually exponential both ways, but it's always exponentially decaying toward the destination value. So going up it's an inverted exponential decay.

But if you're considering something like an amplitude envelope, you may want the rising portions to be an exponential decay (most analog envelope generators work this way, moving to the next stage at a preset threshold). A DX7 has a true exponentially increasing attack (since it's a linear function passed through an exponential lookup table), but it sounds strange and sort of unmusical, like a sound played in reverse.

As suggested in the tutorials, quartic envelopes are a nice compromise. The curves are exponential-like, but they reach the destination values in a finite amount of time.

Thanks for the clarification acreil

It'd be cool to have a nice list somewhere of different envelopes, how they can be made and what situations they're useful for.

@Jwif said:

@ymotion said:

Jwif - the Xn are the values coming from the slider, and Yn are the frequency after a lop was applied?

Almost. Like you said, the Xn graph represents the slider going from 1 to 0 very quickly.

Yn is not showing the frequency but rather the change in sample values (from 1 to 0) over a longer period, this is the output of the [lop~]. How fast this occurs would be the frequency.

just to make sure, the values drop immediately from 1 to 0.12, and then gradually from 0.12 to 0? This sudden drop from 1 to 0.12 does not produce any clicks?

Sorry, I just found that image on google to try and explain it, it's not the actual output of [lop~].

Check out Maelstrom's smoothsteps.mmb patch he linked, it shows a graph of the curve.

OK, thanks Jwif