dynamic string tuning

src/synth/Instruments/PianoString.hpp

@@ -22,22 +22,26 @@ public:
 
 private:
 
+    void recalculateConstants();
+
     // states
+    float frequency_ = 0.0f;
     std::vector<float> stringY_current_;
     std::vector<float> stringY_previous_;
     std::vector<float> stringY_next_;
     std::vector<float> stringX_;
+    bool active_ = false;
 
     // constants
 
     // string parameters
-    size_t segmentCount_ = 30;
+    size_t segmentCount_ = 50;
     static constexpr float rho_ = 8000.0f; // density, steel, kg/m^3
     static constexpr float radius_ = 0.001f; // meters
     static constexpr float stringTension_ = 1200.0f; // string tension, N
-    static constexpr float stiffness_ = 0.001f; // stiffness coefficient
+    static constexpr float stiffness_ = 0.000f; // stiffness coefficient
     float damping_ = 0.5f; // damping coefficient
-    static constexpr float stringLength_ = 1.0f; // length of string
+    static constexpr float stringLength_ = 5.0f; // length of string at lowest frequency (20 hz)
     static constexpr float strikePosition_ = 0.2f; // x of impulse location
     static constexpr float impulseWidth_ = 0.02f; // x of impulse width
     static constexpr float impulseVelocity_ = 10000.0f; // x/t of impulse magnitude
@@ -45,13 +49,12 @@ private:
     float crossSectionalArea_ = pi * std::pow(radius_, 2.0f); // string cross sectional area, assuming circular
     float mu_ = crossSectionalArea_ * rho_; // linear mass density
     float waveVelocity_ = std::sqrt(stringTension_ / mu_); // transverse wave velocity
+    float L_ = 1.0f; // length of string at a given frequency
 
-    // eventually we'll have to dynamically tune our string according to the note that comes in
-    // an alternative is a fully built piano and then it calls voices under the instrument instead of how we do it currently
-    float f0_ = waveVelocity_ / (2.0f * stringLength_); // fundamental frequency of a non-stiff string
-    float f1_ = f0_ * std::sqrt(1.0f + stiffness_); // fundamental frequency of the stiff string
+    // f0_ = waveVelocity_ / (2.0f * stringLength_); // fundamental frequency of a non-stiff string
+    // f1_ = f0_ * std::sqrt(1.0f + stiffness_); // fundamental frequency of the stiff string
 
-    float dx_ = stringLength_ / static_cast<float>(segmentCount_);
+    float dx_ = L_ / static_cast<float>(segmentCount_);
     float dt_ = 1.0f / sampleRate_;
 
     // derived constants