Add bezier curve oscillator

examples/bezier.rs

@@ -0,0 +1,19 @@
+use fon::{chan::Ch16, Audio};
+use twang::tree::{line::Line, Synth};
+
+mod wav;
+//mod plot;
+
+fn main() {
+    // Define waveform
+    let waveform = const { Line(440.0).osc().bezier(Line(1.0)) };
+    // Initialize audio, and create synthesizer
+    let mut audio = Audio::<Ch16, 2>::with_silence(48_000, 48_000 * 5);
+    let mut synth = Synth::new(waveform);
+
+    // Synthesize 5 seconds of audio
+    synth.stream(audio.sink(), &[]);
+    // Plot synthesized audio, and write to a WAV file
+    //plot::write(&audio);
+    wav::write(audio, "bezier.wav").expect("Failed to write WAV file");
+}

src/tree/mod.rs

@@ -52,6 +52,19 @@
 
 macro_rules! const_postfix_waveform {
     () => {
+        /// Postfix helper for wrapping synth instruction with [`osc::Bezier`].
+        ///
+        /// [`osc::Bezier`]: crate::tree::osc::Bezier
+        pub const fn bezier<J>(
+            self,
+            curve: J,
+        ) -> crate::tree::osc::Bezier<Self, J>
+        where
+            J: crate::tree::Wave
+        {
+            crate::tree::osc::Bezier(self, curve)
+        }
+
         /// Postfix helper for wrapping synth instruction with [`osc::Osc`].
         ///
         /// [`osc::Osc`]: crate::tree::osc::Osc
@@ -91,6 +104,7 @@ pub use self::synth::Synth;
     line::Line,
     line::Param,
     for<T: Wave> &T,
+    for<T: Wave, U: Wave> osc::Bezier<T, U>,
     for<T: Wave> osc::Osc<T>,
     for<T: Wave> osc::Sine<T>,
 )]

src/tree/osc/bezier.rs

@@ -0,0 +1,29 @@
+use crate::tree::{Chunk, Wave};
+
+/// Bezier wave
+///
+/// Takes phase (-1 to 1) and curve (-1 to 1) as input
+#[derive(Debug)]
+pub struct Bezier<I, J>(pub I, pub J);
+
+impl<I, J> Wave for Bezier<I, J>
+where
+    I: Wave,
+    J: Wave,
+{
+    fn synthesize(&self, elapsed: u64, interval: u64, vars: &[f32]) -> Chunk {
+        let mut chunk = self.0.synthesize(elapsed, interval, vars);
+        let curve = self.1.synthesize(elapsed, interval, vars);
+
+        for (src, curve) in chunk.0.iter_mut().zip(curve.0.iter()) {
+            let sign = src.signum();
+            let mut output = -src.abs();
+
+            output += 1.0;
+            output = output + output * curve * (output - 1.0) - 1.0;
+            *src = output.copysign(sign);
+        }
+
+        chunk
+    }
+}

src/tree/osc/mod.rs

@@ -2,10 +2,12 @@
 
 #![allow(clippy::module_inception)]
 
+const_postfix_waveform!(Bezier<T, U>, T, U);
 const_postfix_waveform!(Osc<T>, T);
 const_postfix_waveform!(Sine<T>, T);
 
+mod bezier;
 mod osc;
 mod sine;
 
-pub use self::{osc::Osc, sine::Sine};
+pub use self::{bezier::Bezier, osc::Osc, sine::Sine};