[chuck-users] Get the value of an Envelope

[Tom Lieber]

2009/1/20 Andrew C. Smith <acsmith at willamette.edu>:
> I've got some flawed code here, and that's because I'm stuck.  I want
> to dynamically change Gen17's coefficients using an Envelope to get a
> smooth sample-rate transition, but I can't figure out how to use the
> last value from an Envelope and put it into the array to assign to
> cheb.coefs.  How would I do this?  Would I need a sample rate for()
> control?  Thanks.
>
> Andrew
>
> SinOsc drive => Gen17 cheb => dac;
> [1., 0.5, 0.25, 0.125, 0.06] @=> float coefs[];
> 0.2 => cheb.gain;
>
> while(true)
> {
>    Std.rand2(0, 4) => int coef_changed;
>    Std.rand2f(0., 0.99) => float dest;
>
>    coefs => cheb.coefs;
>    Envelope change => coefs[coef_changed];
>
>    change.target(dest);
>    change.duration(50::ms);
>
>    50::ms => now;
> }

The last value is always available via .last(), in this case
change.last(). Unfortunately, the "UGen connection" => and the
"assignment" => are separate operators, so you can't chuck the
envelope into the array. In order to update coefs value using the
envelope, you will have to sample its values manually using a loop
like you said. I think you want something like this:

while(true)
{
   Std.rand2(0, 4) => int coef_changed;
   Std.rand2f(0., 0.99) => float dest;

   coefs => cheb.coefs;
   Envelope change => blackhole;

   change.target(dest);
   change.duration(50::ms);

   // sample envelope every 1ms
   for(now => time t; (now - t) < 50::ms; 1::ms => now) {
      change.last() => coefs[coef_changed];
      // ... use coefs ...
   }
}

-- 
Tom Lieber
http://AllTom.com/