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Plucked.cpp

/***************************************************/
/*! \class Plucked
    \brief STK plucked string model class.

    This class implements a simple plucked string
    physical model based on the Karplus-Strong
    algorithm.

    This is a digital waveguide model, making its
    use possibly subject to patents held by
    Stanford University, Yamaha, and others.
    There exist at least two patents, assigned to
    Stanford, bearing the names of Karplus and/or
    Strong.

    by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
*/
/***************************************************/

#include "Plucked.h"

00022 Plucked :: Plucked(StkFloat lowestFrequency)
{
  length_ = (unsigned long) (Stk::sampleRate() / lowestFrequency + 1);
  loopGain_ = 0.999;
  delayLine_.setMaximumDelay( length_ );
  delayLine_.setDelay( 0.5 * length_ );
  this->clear();
}

00031 Plucked :: ~Plucked()
{
}

00035 void Plucked :: clear()
{
  delayLine_.clear();
  loopFilter_.clear();
  pickFilter_.clear();
}

00042 void Plucked :: setFrequency(StkFloat frequency)
{
  StkFloat freakency = frequency;
  if ( frequency <= 0.0 ) {
    errorString_ << "Plucked::setFrequency: parameter is less than or equal to zero!";
    handleError( StkError::WARNING );
    freakency = 220.0;
  }

  // Delay = length - approximate filter delay.
  StkFloat delay = (Stk::sampleRate() / freakency) - 0.5;
  if ( delay <= 0.0 )
    delay = 0.3;
  else if ( delay > length_ )
    delay = length_;
  delayLine_.setDelay( delay );

  loopGain_ = 0.995 + (freakency * 0.000005);
  if ( loopGain_ >= 1.0 ) loopGain_ = 0.99999;
}

00063 void Plucked :: pluck(StkFloat amplitude)
{
  StkFloat gain = amplitude;
  if ( gain > 1.0 ) {
    errorString_ << "Plucked::pluck: amplitude is greater than 1.0 ... setting to 1.0!";
    handleError( StkError::WARNING );
    gain = 1.0;
  }
  else if ( gain < 0.0 ) {
    errorString_ << "Plucked::pluck: amplitude is < 0.0  ... setting to 0.0!";
    handleError( StkError::WARNING );
    gain = 0.0;
  }

  pickFilter_.setPole( 0.999 - (gain * 0.15) );
  pickFilter_.setGain( gain * 0.5 );
  for (unsigned long i=0; i<length_; i++)
    // Fill delay with noise additively with current contents.
    delayLine_.tick( 0.6 * delayLine_.lastOut() + pickFilter_.tick( noise_.tick() ) );
}

00084 void Plucked :: noteOn(StkFloat frequency, StkFloat amplitude)
{
  this->setFrequency( frequency );
  this->pluck( amplitude );

#if defined(_STK_DEBUG_)
  errorString_ << "Plucked::NoteOn: frequency = " << frequency << ", amplitude = " << amplitude << ".";
  handleError( StkError::DEBUG_WARNING );
#endif
}

00095 void Plucked :: noteOff(StkFloat amplitude)
{
  loopGain_ = 1.0 - amplitude;
  if ( loopGain_ < 0.0 ) {
    errorString_ << "Plucked::noteOff: amplitude is greater than 1.0 ... setting to 1.0!";
    handleError( StkError::WARNING );
    loopGain_ = 0.0;
  }
  else if ( loopGain_ > 1.0 ) {
    errorString_ << "Plucked::noteOff: amplitude is < 0.0  ... setting to 0.0!";
    handleError( StkError::WARNING );
    loopGain_ = (StkFloat) 0.99999;
  }

#if defined(_STK_DEBUG_)
  errorString_ << "Plucked::NoteOff: amplitude = " << amplitude << ".";
  handleError( StkError::DEBUG_WARNING );
#endif
}

StkFloat Plucked :: computeSample()
{
  // Here's the whole inner loop of the instrument!!
  lastOutput_ = delayLine_.tick( loopFilter_.tick( delayLine_.lastOut() * loopGain_ ) ); 
  lastOutput_ *= 3.0;
  return lastOutput_;
}

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