Hi,
here is a first version of my first patch. This is a filter (the filter itself is Moog VCF filter) with a modulation on the resonance (Q factor). It actually sounds more like a tremolo.
////////////////////////////////////////////////////////////////////////////////////////////////////
// 2014-01-12 – blondinou – first version
////////////////////////////////////////////////////////////////////////////////////////////////////
#ifndef __PsycheFilterPatch_hpp__
#define __PsycheFilterPatch_hpp__
#include “StompBox.h”
#include <math.h>
#define TWOPI 6.2831853071f
#define MOD_SPEED 0.14f
#define MOD_LEVEL 1.0f
#define WET_DRY_COMPENSATION 1.5f
#define RES_MIN 0.1f
#define RES_MULT 0.4f
class PsycheFilterPatch : public Patch {
public:
PsycheFilterPatch() :
k(0.0f),
p(0.0f),
r(0.0f),
oldX(0.0f),
oldBuf0(0.0f),
oldBuf1(0.0f),
oldBuf2(0.0f),
x(0.0f),
buf0(0.0f),
buf1(0.0f),
buf2(0.0f),
buf3(0.0f),
phase(0.0f)
{
registerParameter(PARAMETER_A, “Resonance”);
registerParameter(PARAMETER_B, “Cutoff”, “Cutoff frequency”);
registerParameter(PARAMETER_C, “Modulation”, “Resonance modulation speed”);
registerParameter(PARAMETER_D, “Level”, “Effect level”);
sampleRate = getSampleRate();
for (int i = 0; i < 6; i++) { knobs[i] = 0.f; }
}
void processAudio(AudioBuffer &buffer) {
if (parametersChanged()) {
// update filter factors if knobs were moved
updateFactors();
}
// modulation resonance
float q = r;
if (knobs[PARAMETER_C] > 0.0f) {
phase += MOD_SPEED * knobs[PARAMETER_C];
if (phase >= 1.0) {
phase -= 1.0;
}
q += q * MOD_LEVEL * sinf(phase * TWOPI);
}
// apply filter
float level = knobs[PARAMETER_D];
int size = buffer.getSize();
for (int ch = 0; ch < buffer.getChannels(); ++ch) {
float* buf = buffer.getSamples(ch);
for (int i = 0; i < size; i++) {
x = buf[i] – q * buf3;
buf0 = x * p + oldX * p – k * buf0;
buf1 = buf0 * p + oldBuf0 * p – k * buf1;
buf2 = buf1 * p + oldBuf1 * p – k * buf2;
buf3 = buf2 * p + oldBuf2 * p – k * buf3;
buf3 -= (buf3 * buf3 * buf3) / 6.f;
oldX = x;
oldBuf0 = buf0;
oldBuf1 = buf1;
oldBuf2 = buf2;
buf[i] = (1.0f – level) * buf[i] + level * buf3 * WET_DRY_COMPENSATION;
}
}
}
private:
float knobs[6];
float k;
float p;
float r;
float oldX;
float oldBuf0;
float oldBuf1;
float oldBuf2;
float x;
float buf0;
float buf1;
float buf2;
float buf3;
float phase;
double sampleRate;
bool parametersChanged() {
return getParameterValue(PARAMETER_A) != knobs[PARAMETER_A]
|| getParameterValue(PARAMETER_B) != knobs[PARAMETER_B]
|| getParameterValue(PARAMETER_C) != knobs[PARAMETER_C]
|| getParameterValue(PARAMETER_D) != knobs[PARAMETER_D];
}
void updateFactors() {
// update
knobs[PARAMETER_A] = getParameterValue(PARAMETER_A);
knobs[PARAMETER_B] = getParameterValue(PARAMETER_B);
knobs[PARAMETER_C] = getParameterValue(PARAMETER_C);
knobs[PARAMETER_D] = getParameterValue(PARAMETER_D);
// compute filter factors
float resonance = RES_MIN + RES_MULT * knobs[PARAMETER_A];
float cutoff = knobs[PARAMETER_B];
cutoff = (cutoff * 4250.f) + 250.f;
double sampleRate = getSampleRate();
if (sampleRate == 0) {
sampleRate = 44100.0;
}
float f = (cutoff + cutoff) / (float)sampleRate;
p = f * (1.8f – 0.8f * f);
k = p + p – 1.f;
float t = (1.f – p) * 1.386249f;
float t2 = 12.f + t * t;
r = resonance * (t2 + 6.f*t) / (t2 – 6.f * t);
}
};
#endif // __PsycheFilterPatch_hpp__
giom.
