rsc3/doc-schelp/HelpSource/Classes/Phasor.scrbl

#lang scribble/manual
@(require (for-label racket))

@title{Phasor}
 A resettable linear ramp between two levels.@section{categories}
   UGens>Triggers, UGens>Buffer


@section{description}


Phasor is a linear ramp between start and end values. When its trigger
input crosses from non-positive to positive, Phasor's output will jump to
its reset position. Upon reaching the end of its ramp Phasor will wrap
back to its start.


@section{note}
 
N.B. Since end is defined as the wrap point, its value is never
actually output.
::

@section{note}
 
If one wants Phasor to output a signal with frequency teletype::freq:: oscillating between teletype::start:: and teletype::end::, then the rate should be teletype::(end - start) * freq / sr:: where teletype::sr:: is the sampling rate.
::

Phasor is commonly used as an index control with  link::Classes/BufRd::
and  link::Classes/BufWr:: .


@section{classmethods}
 

@section{method}
 ar, kr

@section{argument}
 trig

When triggered, jump to resetPos (default: 0, equivalent to
start).


@section{argument}
 rate

The amount of change per sample, i.e at a rate of 1 the value of
each sample will be 1 greater than the preceding sample.


@section{argument}
 start

Start point of the ramp.


@section{argument}
 end

End point of the ramp.


@section{argument}
 resetPos

The value to jump to upon receiving a trigger.


@section{Examples}
 


@racketblock[

// phasor controls sine frequency: end frequency matches a second sine wave.

(
{ var trig, rate, x, sr;
	rate = MouseX.kr(0.2, 2, 1);
	trig = Impulse.ar(rate);
	sr = SampleRate.ir;
	x = Phasor.ar(trig, rate / sr);
	SinOsc.ar(
		[
			LinLin.kr(x, 0, 1, 600, 1000), // convert range from 0..1 to 600..1000
			1000 // constant second frequency
		], 0, 0.2)

}.play;
)


// two phasors control two sine frequencies: mouse y controls resetPos of the second
(
{ var trig, rate, x, sr;
	rate = MouseX.kr(1, 200, 1);
	trig = Impulse.ar(rate);
	sr = SampleRate.ir;
	x = Phasor.ar(trig, rate / sr, 0, 1, [0, MouseY.kr(0, 1)]);
	SinOsc.ar(x * 500 + 500, 0, 0.2)
}.play;
)


// use phasor to index into a sound file

// allocate a buffer with a sound file
b = Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav");

// simple playback (more examples: see BufRd)
// Start and end here are defined as 0 and the number of frames in the buffer.
// This means that the Phasor will output values from 0 to numFrames - 1 before looping,
// which is perfect for driving BufRd. (See note above)
{ BufRd.ar(1, b.bufnum, Phasor.ar(0, BufRateScale.kr(b.bufnum), 0, BufFrames.kr(b.bufnum))) }.play;


// two phasors control two sound file positions: mouse y controls resetPos of the second
(
{ var trig, rate, framesInBuffer;
	rate = MouseX.kr(0.1, 100, 1);
	trig = Impulse.ar(rate);
	framesInBuffer = BufFrames.kr(b.bufnum);
	x = Phasor.ar(trig, BufRateScale.kr(b.bufnum), 0, framesInBuffer,
		[0, MouseY.kr(0, framesInBuffer)]);
	BufRd.ar(1, b.bufnum, x);
}.play;
)

::
]