Hi Yoann,
You can simply multiply the functions with their conditions:
f(x) = (x < LowerThreshold) * LowerSignal(x) + ((x >= LowerThreshold)
& (x <= UpperThreshold)) * LinearSignal + (x > UpperThreshold) *
UpperSignal
process = f
Hope this works for you!
Flo
Am So., 22. Nov. 2020 um 12:39 Uhr schrieb yoann.le.bor...@gmail.com
<yoann.le.bor...@gmail.com>:
>
>
> Hi!
>
> I'm currently trying to create a waveshaper using different functions
> according to its input signal and I'm stuck at what would be the best
> approach doing so using Faust.
>
> Here is the concept:
>
> If the signal is x=s(t), the waveshaper is F(x) where:
> F(x) = log10(x)+1 when x > e/10
> F(x) = 10x/(e*log(10)) when x >= e/10 and x >=- e/10
> F(x) = -log10(-x)-1 when x < -e/10
>
> Here is a quick and incomplete sketch for further discussions:
> import("stdfaust.lib");
> UpperSignal = _ : log10 : _+1 : _ ; // when x > e/10
> LinearSignal = _ : _*1.59768011306 : _ ; // when x >= e/10 and x >=- e/10
> LowerSignal = _ : _*-1 : log10 : _*-1 : _-1 : _ ; //when x < - e/10
> UpperThreshold = 0.27182818284 ; // e/10
> LowerThreshold = -0.27182818284 ; // -e/10
> process = _ <: UpperSignal,LinearSignal,LowerSignal:>_;
>
> The attached picture is a visual representation where the dashed orange
> lines are thresholds, red sections of the curve are UpperSignal and
> LowerSignal and the black section of the curve is LinearSignal.
>
> This is an example of a commonly used method for waveshaping where you
> use different functions according to the input signal.
>
> Here are two interesting articles using this method with various degrees
> of complexity:
> -
> https://medium.com/@jatinchowdhury18/complex-nonlinearities-episode-1-double-soft-clipper-5ce826fa82d6
> - https://www.ampbooks.com/mobile/dsp/preamp/
>
> In a non functional language, I would have used a classic if/then/else
> but, as specified in the faust manual:
> "WARNING: since select2 is strict (always evaluating both branches), the
> resulting if does not have the usual "lazy" semantic of the C if form,
> and thus cannot be used to protect against forbidden computations like
> division-by-zero for instance."
>
> Ideally, only one of the three functions should be computed by
> correctly routing the input signal (using ! or another mean).
>
> What would be the Faustian way to do so?
>
> Best regards,
> Yoann
>
>
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--
Florian Hülsmann
<f...@cbix.de>
http://cbix.de
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