From b75bdf9ddcf2d6fc40782d519dfefad2a0654c25 Mon Sep 17 00:00:00 2001
From: Jacob Lee <jacob@unabridgedsoftware.com>
Date: Tue, 2 Nov 2021 23:03:05 -0400
Subject: Bending it like Beckham

---
 klangfarb/Main.tscn         |   3 ++-
 klangfarb/libklangfarbrs.so | Bin 20146368 -> 20305280 bytes
 klangfarb/main.gd           |   3 ++-
 klangfarbrs/src/lib.rs      |  25 ++++++++++++++++++++++---
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/klangfarb/Main.tscn b/klangfarb/Main.tscn
index 95d51f7..896aa8c 100644
--- a/klangfarb/Main.tscn
+++ b/klangfarb/Main.tscn
@@ -6,5 +6,6 @@
 
 [node name="Audio" type="AudioStreamPlayer"]
 stream = SubResource( 1 )
-volume_db = -7.38
+volume_db = -13.216
 script = ExtResource( 2 )
+freq = 130.0
diff --git a/klangfarb/libklangfarbrs.so b/klangfarb/libklangfarbrs.so
index 9070316..ee0ba0e 100755
Binary files a/klangfarb/libklangfarbrs.so and b/klangfarb/libklangfarbrs.so differ
diff --git a/klangfarb/main.gd b/klangfarb/main.gd
index cf3d8c1..439bb50 100644
--- a/klangfarb/main.gd
+++ b/klangfarb/main.gd
@@ -2,6 +2,7 @@ extends AudioStreamPlayer
 
 # controllable frequency interface
 export(float, 20, 8000, 5) var freq = 440.0
+export(float, 0, 1, 0.1) var bend = 0.5
 # control wave form
 export(String, "sine", "square", "triangle", "sawtooth") var waveform = "sine"
 
@@ -21,7 +22,7 @@ func _fill_buffer() -> void:
 		# ask Rust to generate N frames at freq
 		# Array<Vector2> gets pushed to the 
 		# playback stream buffer
-		playback.push_buffer(wave.frames(freq, to_fill)) 
+		playback.push_buffer(wave.frames(freq, to_fill, bend)) 
 
 func _check_waveform():
 	if waveform == "square":
diff --git a/klangfarbrs/src/lib.rs b/klangfarbrs/src/lib.rs
index 8fb773d..9ba44d9 100644
--- a/klangfarbrs/src/lib.rs
+++ b/klangfarbrs/src/lib.rs
@@ -66,10 +66,28 @@ fn generate_sample(osc: &Osc) -> f32 {
 /// for a given wave form. Since audio signals are periodic, we can just calculate
 /// the first cycle of a wave repeatedly. This also prevents pitch drift caused by
 /// floating point errors over time.
-fn calculate_phase(osc: &Osc, frequency: f32) -> f32 {
+fn next_phase(osc: &Osc, frequency: f32) -> f32 {
     (osc.phase + (frequency / osc.sample_rate)) % 1.0
 }
 
+// for (i = 0; i < nframes; ++i) {
+//     if (in[i] < x0)
+//       out[i] = (y0/x0)*in[i];
+//     else
+//       out[i] = ((1-y0)/(1-x0)) * (in[i] - x0) + y0;
+//   }
+fn bend_phase(osc: &Osc, frequency: f32, bend_factor: f32) -> f32 {
+    let current_phase = osc.phase;
+    let next_phase = next_phase(osc, frequency);
+    let step = next_phase - current_phase;
+
+    if osc.phase < bend_factor {
+        step * 2.0
+    } else {
+        step / 2.0
+    }
+}
+
 /// # Examples
 ///
 /// It is more work than benefit to figure out how to instantiate a Godot object (Node)
@@ -126,13 +144,14 @@ impl Osc {
     }
 
     #[export]
-    pub fn frames(&mut self, _owner: &Node, frequency: f32, duration: i32) -> TypedArray<Vector2> {
+    pub fn frames(&mut self, _owner: &Node, frequency: f32, duration: i32, bend_factor: f32) -> TypedArray<Vector2> {
         let mut frames = TypedArray::new();
 
         for _i in 0..duration {
             let sample = generate_sample(&self);
             frames.push(Vector2::new(sample, sample));
-            self.phase = calculate_phase(&self, frequency);
+            // self.phase = next_phase(&self, frequency);
+            self.phase = self.phase + bend_phase(&self, frequency, bend_factor)
         }
 
         return frames
-- 
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