일단 간단하게라도 피아노 VSTI를 만들어볼려고 한다.

위 파형을 통해 소리가 나는 피아노 가상악기를 제젝할 것이다.

그리고 제작했다.

핵심코드는 다음과 같다.

class MainComponent  : public juce::AudioAppComponent
{
public:
    //==============================================================================
    MainComponent()
    {
        // Make sure you set the size of the component after
        // you add any child components.
        setSize (800, 600);

        // Some platforms require permissions to open input channels so request that here
        if (juce::RuntimePermissions::isRequired (juce::RuntimePermissions::recordAudio)
            && ! juce::RuntimePermissions::isGranted (juce::RuntimePermissions::recordAudio))
        {
            juce::RuntimePermissions::request (juce::RuntimePermissions::recordAudio,
                                               [&] (bool granted) { setAudioChannels (granted ? 2 : 0, 2); });
        }
        else
        {
            // Specify the number of input and output channels that we want to open
            setAudioChannels (2, 2);
        }
    }

struct  SineWaveSound : public juce::SynthesiserSound
{
    SineWaveSound() {}

    bool appliesToNote(int) override {return  true;}
    bool appliesToChannel(int) override {return true;}
};

struct SineWaveVoice   : public juce::SynthesiserVoice
{
    SineWaveVoice() {}

    bool canPlaySound (juce::SynthesiserSound* sound) override
    {
        return dynamic_cast<SineWaveSound*> (sound) != nullptr;
    }

    void startNote (int midiNoteNumber, float velocity,
                    juce::SynthesiserSound*, int /*currentPitchWheelPosition*/) override
    {
        currentAngle = 0.0;
        level = velocity * 0.15;
        tailOff = 0.0;

        auto cyclesPerSecond = juce::MidiMessage::getMidiNoteInHertz (midiNoteNumber);
        auto cyclesPerSample = cyclesPerSecond / getSampleRate();

        angleDelta = cyclesPerSample * 2.0 * juce::MathConstants<double>::pi;
    }

    void stopNote (float /*velocity*/, bool allowTailOff) override
    {
        if (allowTailOff)
        {
            if (tailOff == 0.0)
                tailOff = 1.0;
        }
        else
        {
            clearCurrentNote();
            angleDelta = 0.0;
        }
    }

    void pitchWheelMoved (int) override      {}
    void controllerMoved (int, int) override {}

    void renderNextBlock (juce::AudioSampleBuffer& outputBuffer, int startSample, int numSamples) override
    {
        if (angleDelta != 0.0)
        {
            if (tailOff > 0.0) // [7]
            {
                while (--numSamples >= 0)
                {
                    auto currentSample = (float) (std::sin (currentAngle) * level * tailOff);

                    for (auto i = outputBuffer.getNumChannels(); --i >= 0;)
                        outputBuffer.addSample (i, startSample, currentSample);

                    currentAngle += angleDelta;
                    ++startSample;

                    tailOff *= 0.99; // [8]

                    if (tailOff <= 0.005)
                    {
                        clearCurrentNote(); // [9]

                        angleDelta = 0.0;
                        break;
                    }
                }
            }
            else
            {
                while (--numSamples >= 0) // [6]
                {
                    auto currentSample = (float) (std::sin (currentAngle) * level);

                    for (auto i = outputBuffer.getNumChannels(); --i >= 0;)
                        outputBuffer.addSample (i, startSample, currentSample);

                    currentAngle += angleDelta;
                    ++startSample;
                }
            }
        }
    }

private:
    double currentAngle = 0.0, angleDelta = 0.0, level = 0.0, tailOff = 0.0;
};