private:

const static int DDS_LENGTH = 1<<14;

const static int WIN_LENGTH = 1<<14;

const static int TONES = 12;

float acc[TONES];

float inc[TONES];

Window amp;

FloatArray sine;

public:

ShepardTonesPatch(){

registerParameter(PARAMETER_A, "Pitch");

registerParameter(PARAMETER_B, "Range");

registerParameter(PARAMETER_C, "Tones");

registerParameter(PARAMETER_D, "Rate");

sine = FloatArray::create(DDS_LENGTH);

for(int i=0; i<DDS_LENGTH; ++i)

sine[i] = sin(2*M_PI*i/(DDS_LENGTH-1));

amp = Window::create(Window::HannWindow, WIN_LENGTH);

amp.multiply(2.0/TONES);

for(int i=0; i<TONES; i++)

acc[i] = 0.0;

inc[0] = 0.001;

for(int i=1; i<TONES; i++)

inc[i] = inc[i-1]*2;

// sets tones one octave apart

}

~ShepardTonesPatch(){

FloatArray::destroy(sine);

Window::destroy(amp);

}

float getAmplitude(float inc){

uint32_t index = inc*(WIN_LENGTH-1);

index = min(index, WIN_LENGTH-1);

return amp[index];

}

float getWave(float phase){

uint32_t index = phase*(DDS_LENGTH-1);

index = min(index, DDS_LENGTH-1);

return sine[index];

}

void processAudio(AudioBuffer& buf){

float minf = getParameterValue(PARAMETER_A)*0.1 + 0.001;

float maxf = min(0.4, minf + getParameterValue(PARAMETER_B)*0.2);

// range should be exponentially related to minf

// int tones = getParameterValue(PARAMETER_C)*(TONES-1) + 1;

int tones = 12;

float spread = getParameterValue(PARAMETER_C) + 1.0;

float rate = 1.0 + (getParameterValue(PARAMETER_D) - 0.5)*0.00002;

int size = buf.getSize();

FloatArray out = buf.getSamples(LEFT_CHANNEL);

float amp;

for(int t=1; t<tones; ++t)

inc[t] = inc[t-1]*spread;

for(int i=0; i<size; ++i){

for(int t=0; t<tones; ++t){

amp = getAmplitude((inc[t]-minf)/(maxf-minf));

out[i] += amp * getWave(acc[t]);

acc[t] += inc[t];

if(acc[t] > 1.0)

acc[t] -= 1.0;

else if(acc[t] < 0.0)

acc[t] += 1.0;

inc[t] *= rate;

}

}

if(inc[0] > maxf)

inc[0] = minf;

// while(inc[0] > minf)

// inc[0] *= 0.5;

else if(inc[0] < minf)

inc[0] = maxf;

// while(inc[0] < maxf)

// inc[0] *= 2.0;

}