WDL/sinewavegen.h

   1 #ifndef _WDL_SINEWAVEGEN_H_
   2 #define _WDL_SINEWAVEGEN_H_
   3
   4
   5 // note: calling new WDL_SineWaveGenerator isnt strictly necessary, you can also do WDL_SineWaveGenerator *gens = (WDL_SineWaveGenerator *)malloc(512*sizeof(WDL_SineWaveGenerator));
   6 // as long as you call Reset() and SetFreq() it should be fine.
   7
   8
   9 // note: won't really work for high frequencies...
  10
  11 class WDL_SineWaveGenerator
  12 {
  13   double m_lastfreq;
  14   double m_mul1,m_mul2;
  15   double m_pos,m_vel;
  16
  17 public:
  18   WDL_SineWaveGenerator() { Reset(); m_mul1=m_mul2=m_pos=m_vel=0.0; }
  19   ~WDL_SineWaveGenerator() { }
  20
  21   void Reset() { m_lastfreq=0.0; } // must call this before anything
  22
  23   void SetFreq(double freq) // be sure to call this before calling Gen(), or on freq change, or after a Reset()
  24                             // freq is frequency/(samplerate*0.5) (so 0..1 is valid, though over 0.3 is probably not a good idea)
  25   {
  26     freq*=3.1415926535897932384626433832795; // scale to freq*PI
  27
  28     if (m_lastfreq<=0.0)
  29     {
  30       m_pos=0.0;
  31       m_vel = 1.0/freq;
  32     }
  33     else
  34     {
  35       if (freq==m_lastfreq) return;
  36       m_vel *= m_lastfreq/freq;
  37     }
  38     m_lastfreq=freq;
  39
  40     double tmp2 = 1.0/(1.0+(freq*=freq));
  41     m_mul1 = (1.0-freq)*tmp2;
  42     m_mul2 = freq*2.0*tmp2;
  43   }
  44
  45   double Gen() // returns sine
  46   {
  47     double rv=m_pos;
  48     m_vel -= rv + (m_pos = rv*m_mul1 + m_vel*m_mul2);
  49     return rv;
  50   }
  51
  52   double GetNextCos()  // call BEFORE Gen() if you want the cosine of the next value
  53   {
  54     return m_vel * m_lastfreq;
  55   }
  56
  57 };
  58
  59 #endif