rmx-19/Source/SynthEngine.cpp

#include "SynthEngine.h"

SynthEngine::SynthEngine()  { rng.setSeedRandomly(); }
SynthEngine::~SynthEngine() {}

void SynthEngine::setSampleRate (double s)
{
    sr = s;
}

float SynthEngine::osc (int wave, double ph)
{
    switch (wave)
    {
        case 0:  return (float) std::sin (ph * 2.0 * juce::MathConstants<double>::pi);
        case 1:  return (float) (ph < 0.5 ? 4.0 * ph - 1.0 : 3.0 - 4.0 * ph);
        case 2:  return (float) (1.0 - 2.0 * ph);
        case 3:  return (float) (ph < 0.5 ? -1.0 : 1.0);
        case 4:  return rng.nextFloat() * 2.0f - 1.0f;
        default: return 0.0f;
    }
}

void SynthEngine::allNotesOff (bool immediate)
{
    for (auto& v : voices)
    {
        if (v.active)
        {
            if (immediate) v.active = false;
            else           v.amp.noteOff();
        }
    }
    sustainedNotes.clear();
    if (immediate) active = 0;
}

void SynthEngine::sustainPedal (bool down)
{
    pedal = down;
    if (! down)
    {
        for (auto n : sustainedNotes)
            for (auto& v : voices)
                if (v.active && v.note == n)
                    v.amp.noteOff();
        sustainedNotes.clear();
    }
}

void SynthEngine::pitchBend (float cents) { bendCents = cents; }
void SynthEngine::modWheel (float v)      { mod = juce::jlimit (0.0f, 1.0f, v); }

SynthEngine::Voice* SynthEngine::acquireVoice()
{
    const int lim = juce::jlimit (1, maxVoice, polyLimit);
    for (int i = 0; i < lim; ++i)
        if (! voices[i].active)
            return &voices[i];

    stealIdx = (stealIdx + 1) % lim;
    Voice* v = &voices[stealIdx];
    if (v->active)
    {
        v->amp.noteOff();
        v->flt.noteOff();
    }
    return v;
}

void SynthEngine::noteOn (int midiNote, float velocity)
{
    const float noteFreq = (float) (440.0 * std::exp2 ((midiNote - 69.0) / 12.0));
    Voice* v = acquireVoice();
    const bool fresh = ! v->active;
    v->active = true;
    v->note = midiNote;
    v->vel = 1.0f - std::pow (1.0f - velocity, 1.35f);
    v->curFreq  = (lastGlide > 0.001f && lastNoteFreq > 0.0f) ? lastNoteFreq : noteFreq;
    v->targetFreq = noteFreq;
    v->ph1 = rng.nextDouble() * 0.5;
    v->ph2 = rng.nextDouble() * 0.5;
    v->lfoPh = rng.nextDouble();
    v->lfoIdx = 0;
    v->lfoSH = rng.nextFloat() * 2.0f - 1.0f;
    v->lp = v->bp = 0.0f;
    v->fcSm = 0.0f;
    v->outSmooth = 0.0f;

    const float p = juce::jlimit (-1.0f, 1.0f, lastPan + (rng.nextFloat() - 0.5f) * 0.1f);
    const float ang = (p + 1.0f) * juce::MathConstants<float>::pi * 0.25f;
    const float mag = 0.7071f + 0.25f * rng.nextFloat();
    v->panL = std::cos (ang) * mag;
    v->panR = std::sin (ang) * mag;

    v->amp.reset(); v->flt.reset();
    v->amp.noteOn(); v->flt.noteOn();
    lastNoteFreq = noteFreq;
    if (fresh) ++active;
}

void SynthEngine::noteOff (int midiNote)
{
    if (pedal)
    {
        if (! sustainedNotes.contains (midiNote))
            sustainedNotes.add (midiNote);
        return;
    }
    for (auto& v : voices)
        if (v.active && v.note == midiNote)
            v.amp.noteOff();
}

void SynthEngine::render (const VParams& p, float* left, float* right, int num)
{
    for (auto& v : voices)
    {
        v.amp.setRates (p.ampA, p.ampD, p.ampS, p.ampR, sr);
        v.flt.setRates (p.fA,    p.fD,    p.fS,    p.fR,    sr);
    }
    lastGlide = p.glide;
    lastPan   = p.pan;
    polyLimit = juce::jlimit (1, maxVoice, (int) p.poly);

    const float glideRate = p.glide <= 0.001f ? 1.0f
                         : 1.0f - std::exp (-1.0f / (p.glide * (float) sr));
    const float detuneRatio2 = std::exp2f (p.detune / 1200.0f);
    const float detuneRatio1 = std::exp2f (p.detune1 / 1200.0f);
    const float tuneRatio   = std::exp2f (p.tune / 12.0f);
    const float maxFc = 0.4f * (float) sr;
    const float minFc = 30.0f;

    for (int s = 0; s < num; ++s)
    {
        float mixL = 0.0f, mixR = 0.0f;
        int activeCount = 0;
        for (auto& v : voices)
            if (v.active) ++activeCount;
        const float voiceGain = activeCount > 1 ? 1.0f / std::sqrtf ((float) activeCount) : 1.0f;

        for (auto& v : voices)
        {
            if (! v.active)
                continue;

            if (p.glide > 0.001f)
                v.curFreq += (v.targetFreq - v.curFreq) * glideRate;
            else
                v.curFreq = v.targetFreq;

            // LFO
            v.lfoPh += (double) p.lfoRate / sr;
            while (v.lfoPh >= 1.0)
            {
                v.lfoPh -= 1.0;
                v.lfoIdx++;
                v.lfoSH = rng.nextFloat() * 2.0f - 1.0f;
            }

            float lfo = 0.0f;
            switch ((int) p.lfoShape)
            {
                case 0: lfo = (float) std::sin (v.lfoPh * 2.0 * juce::MathConstants<double>::pi); break;
                case 1: lfo = (float) (v.lfoPh < 0.5 ? 4.0 * v.lfoPh - 1.0 : 3.0 - 4.0 * v.lfoPh); break;
                case 2: lfo = v.lfoPh < 0.5 ? -1.0f : 1.0f; break;
                case 3: lfo = v.lfoSH; break;
                default: lfo = 0.0f; break;
            }

            // frequency, vibrato, bend, tune
            float freq = v.curFreq * tuneRatio;
            if ((int) p.lfoTarget == 1)
                freq *= std::exp2f (lfo * p.lfoDepth * 1.6f / 12.0f);
            if (bendSmooth != bendCents)
                bendSmooth += (bendCents - bendSmooth) * 0.08f;
            freq *= std::exp2f (bendSmooth / 1200.0f);

            const float d1 = (float) (freq / sr) * detuneRatio1;
            const float d2 = (float) (freq / sr) * detuneRatio2;

            v.ph1 += d1; if (v.ph1 >= 1.0) v.ph1 -= 1.0;
            v.ph2 += d2; if (v.ph2 >= 1.0) v.ph2 -= 1.0;

            const float o1 = osc ((int) p.osc1w, v.ph1);
            const float o2 = osc ((int) p.osc2w, v.ph2);
            const float mixb = p.oscMix * 0.01f;
            float sig = o1 * (1.0f - mixb) + o2 * mixb;

            const float fe = v.flt.next();

            // cutoff with keytrack + filter envelope + LFO + mod wheel
            float fc = p.fltCut;
            fc *= std::exp2f (p.fltKey * 0.01f * std::log2f (freq / 261.6256f));
            fc *= std::exp2f (p.fltEnv * 0.01f * fe * std::log2f (maxFc / fc));
            if ((int) p.lfoTarget == 0)
                fc *= std::exp2f (lfo * p.lfoDepth * 10.0f / 12.0f);
            fc *= std::exp2f (mod);
            fc = std::min (maxFc, std::max (minFc, fc));
            v.fcSm += (fc - v.fcSm) * 0.25f;
            fc = v.fcSm;

            // SVF (cap f1 to keep the Chamberlin structure stable; past ~1.5 the
            // resonance feedback can self-oscillate and sputter at maxed cutoff+res)
            const float f1 = std::min (1.50f, 2.0f * std::sin (juce::MathConstants<float>::pi * fc / (float) sr));
            const float q1 = 1.0f / (1.0f + p.fltRes * 3.0f);
            v.f1c = f1;
            const float hp = sig - v.lp - q1 * v.bp;
            v.bp += f1 * hp;
            v.lp += f1 * v.bp;

            float filtered = sig;
            switch ((int) p.fltType)
            {
                case 1: filtered = v.lp; break;
                case 2: filtered = v.bp; break;
                case 3: filtered = hp;   break;
                default: break;
            }

            // amplitude envelope (+ tremolo if LFO targets amp)
            const float ae = v.amp.next();
            float ampMod = 1.0f;
            if ((int) p.lfoTarget == 2)
                ampMod = 1.0f - p.lfoDepth * 0.5f * (1.0f + lfo);

            v.outSmooth += (filtered - v.outSmooth) * 0.12f;
            float o = v.outSmooth * (ae * ampMod) * v.vel * voiceGain;
            if (! std::isfinite (o)) o = 0.0f;

            mixL += o * v.panL;
            mixR += o * v.panR;

            if (v.amp.getState() == Env::Off)
            {
                v.active = false;
                if (active > 0) --active;
            }
        }

        if (! std::isfinite (mixL)) mixL = 0.0f;
        if (! std::isfinite (mixR)) mixR = 0.0f;

        // Soft limiter before tanh for cleaner saturation
        mixL = std::tanh (mixL * 0.8f);
        mixR = std::tanh (mixR * 0.8f);

        left[s]  += mixL;
        right[s] += mixR;
    }
}