76 lines
2.6 KiB
C++
76 lines
2.6 KiB
C++
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#pragma once
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#include <cmath>
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#include "synth/Instruments/Instrument.hpp"
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class PianoString : public Instrument {
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public:
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PianoString() = default;
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PianoString(ConfigService* config, LoggerService* logger);
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~PianoString() = default;
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void noteOn(float frequency, float velocity) override;
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void noteOff() override;
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bool isActive() override;
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float process(bool& scopeTrigger) override;
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private:
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void recalculateConstants();
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// states
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float frequency_ = 0.0f;
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std::vector<float> stringY_current_;
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std::vector<float> stringY_previous_;
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std::vector<float> stringY_next_;
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std::vector<float> stringX_;
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bool active_ = false;
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// constants
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// string parameters
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size_t segmentCount_ = 80;
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static constexpr float rho_ = 8000.0f; // density, steel, kg/m^3
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static constexpr float radius_ = 0.001f; // meters
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static constexpr float stringTension_ = 1200.0f; // string tension, N
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static constexpr float stiffness_ = 0.0f; // stiffness coefficient
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float damping_ = 0.5f; // damping coefficient
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static constexpr float stringLength_ = 4.0f; // length of string at lowest frequency (20 hz)
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static constexpr float strikePosition_ = 0.8f; // x of impulse location
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static constexpr float impulseWidth_ = 0.1f; // x% of impulse width
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static constexpr float impulseVelocity_ = 10000.0f; // x/t of impulse magnitude
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static constexpr float samplePosition_ = 0.2f; // percentage along L of sampling for audio
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float crossSectionalArea_ = pi * std::pow(radius_, 2.0f); // string cross sectional area, assuming circular
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float mu_ = crossSectionalArea_ * rho_; // linear mass density
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float waveVelocity_ = std::sqrt(stringTension_ / mu_); // transverse wave velocity
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float L_ = 1.0f; // length of string at a given frequency
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float gain_ = 0.5f;
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// f0_ = waveVelocity_ / (2.0f * stringLength_); // fundamental frequency of a non-stiff string
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// f1_ = f0_ * std::sqrt(1.0f + stiffness_); // fundamental frequency of the stiff string
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uint32_t samplingSteps_ = 1;
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float phaseTracker_ = 0.0f;
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float dx_ = L_ / static_cast<float>(segmentCount_);
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float dt_ = 1.0f / sampleRate_;
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// derived constants
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float r1_ = waveVelocity_ * dt_/dx_;
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float r2_ = std::pow(waveVelocity_ * dt_/dx_, 2.0f);
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float s1_ = stiffness_ * dt_/std::pow(dx_, 2.0f);
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float s2_ = std::pow(stiffness_ * dt_/std::pow(dx_, 2.0f), 2.0f);
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float a1_ = 2.0f - 2.0f * damping_ * dt_;
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float a2_ = 2.0f * damping_ * dt_ - 1.0f;
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// keeping track of the string's activeness
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float rms_ = 0.0f;
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};
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