Add levels and more DistortionModes

Author: OpenSauce

presets/clean.json

@@ -5,5 +5,6 @@
   "gate_threshold": 0.02,
   "lowpass_cutoff": 6000.0,
   "highpass_cutoff": 120.0,
-  "mode": "Sigmoid"
+  "mode": "Sigmoid",
+  "level": 0.5
 }

presets/metal.json

@@ -1,8 +1,9 @@
 {
-  "gain": 10.0,
+  "gain": 2.0,
   "drive": 50.0,
   "gate_threshold": 0.02,
   "lowpass_cutoff": 6000.0,
   "highpass_cutoff": 120.0,
-  "mode": "Sigmoid"
+  "mode": "Polynomial",
+  "level": 0.5
 }

src/amp.rs

@@ -8,6 +8,10 @@ pub enum DistortionMode {
     HardClip,
     Asymmetric,
     Sigmoid,
+    ArcTan,
+    Polynomial,
+    DiodeLike,
+    WaveFold,
 }
 
 pub struct Amp {
@@ -20,6 +24,7 @@ pub struct Amp {
     highpass_prev: f32,
     distorted_prev: f32,
     mode: DistortionMode,
+    level: f32,
 }
 
 #[derive(Debug, Clone, Copy, Serialize, Deserialize)]
@@ -30,6 +35,7 @@ pub struct AmpConfig {
     pub lowpass_cutoff: f32,
     pub highpass_cutoff: f32,
     pub mode: DistortionMode,
+    pub level: f32,
 }
 
 impl Amp {
@@ -41,6 +47,7 @@ impl Amp {
             lowpass_cutoff,
             highpass_cutoff,
             mode,
+            level,
         } = config;
 
         let rc_lp = 1.0 / (2.0 * PI * lowpass_cutoff);
@@ -59,6 +66,7 @@ impl Amp {
             highpass_prev: 0.0,
             distorted_prev: 0.0,
             mode,
+            level,
         }
     }
 
@@ -75,16 +83,47 @@ impl Amp {
             DistortionMode::HardClip => gated.clamp(-1.0, 1.0),
             DistortionMode::Asymmetric => gated.tanh() + 0.3 * gated,
             DistortionMode::Sigmoid => gated / (1.0 + gated.abs()),
+
+            DistortionMode::ArcTan => gated.atan() * (2.0 / PI),
+
+            DistortionMode::Polynomial => {
+                let x = gated;
+                let poly = (3.0 * x - x.powi(3)) * 0.5;
+                poly.clamp(-1.0, 1.0)
+            }
+
+            DistortionMode::DiodeLike => {
+                if gated >= 0.0 {
+                    gated / (1.0 + gated.abs())
+                } else {
+                    0.3 * gated
+                }
+            }
+
+            DistortionMode::WaveFold => foldback(gated, 1.0),
         };
 
+        // Highpass filter (removing DC or very low freq)
         let highpassed =
             self.highpass_alpha * (self.highpass_prev + distorted - self.distorted_prev);
         self.distorted_prev = distorted;
         self.highpass_prev = highpassed;
 
+        // Lowpass filter (smooth out harshness at very high freq)
         let filtered = self.lowpass_prev + self.lowpass_alpha * (highpassed - self.lowpass_prev);
         self.lowpass_prev = filtered;
 
-        filtered
+        // Apply final level
+        filtered * self.level
+    }
+}
+
+fn foldback(mut x: f32, limit: f32) -> f32 {
+    while x > limit {
+        x = 2.0 * limit - x;
+    }
+    while x < -limit {
+        x = -2.0 * limit - x;
     }
+    x
 }

src/processor.rs

@@ -71,8 +71,8 @@ impl Processor {
         };
 
         let upsampler = SincFixedIn::<f32>::new(
-            oversample_factor as f64,
-            1.0,
+            oversample_factor as f64, // The resample ratio
+            1.0,                      // Tolerance
             interp_params,
             max_chunk_size as usize,
             channels,