[PD] log function in slider

Alexandre Torres Porres porres at gmail.com
Mon Mar 17 06:21:34 CET 2014

Hi Roman. This is turning out trickier than I thought. A friend explained
the code to me and got to the following equation, with min/max values as
0.01 and 1 respectively.

[expr 0.01 * exp((log(1 / 0.01) / 0.01) * $f1 * 0.01)]

For what I've checked, it seems to behave like your patch. But it doesn't
do the trick I'm looking for yet. I sent a patch earlier, and I'm sending
it back again.

The goal is to connect a linear slider to an [expr] (with this so called
"log" function) and then to another linear slider. The idea then is that
this second slider behaves as one that was set as being "log".

In the patch attached I was able to emulate it poorly with [pow 0.25], but
that was before reaching the list. See that if I use this expr function
from the code or your patch it presents quite a different behavior.

maybe it is some sort of inversion of this equation, not sure. Apparently
this code converts the "log" function values to linear and I'm hoping to
get the exact opposite. Got it?

Thanks for looking into this

2014-03-12 4:38 GMT-03:00 Roman Haefeli <reduzent at gmail.com>:

> On Don, 2014-03-06 at 21:37 -0300, Alexandre Torres Porres wrote:
> > hi folks, out of curiosity, what's the exact log function used in the
> > slider? I'd like to emulate it.
> I am not sure, if this is what you want. It converts the incoming linear
> range between 0 and 1 to a logarithmic range specified by $1 and $2,
> respectively by the second and third inlet. They behave like the lower
> and upper bound specified in the [vslider]/[hslider] classes.
> https://raw.github.com/reduzent/netpd2-patches/master/abs/rh_scalelog.pd
> Roman
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