init

Source/DSP/Distortion.h

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+#pragma once
+#include <cmath>
+#include <algorithm>
+
+enum class DistortionType { SoftClip = 0, HardClip, Foldback, Overdrive, NumTypes };
+
+class Distortion {
+public:
+    void prepare(double /*sr*/) {}
+
+    void setParameters(DistortionType type, float amount, float mix) {
+        distType = type;
+        distAmount = amount;
+        dryWet = mix;
+    }
+
+    float process(float input) {
+        float driven = input * (1.0f + distAmount * 9.0f);
+        float wet = 0.0f;
+
+        switch (distType) {
+            case DistortionType::SoftClip:
+                wet = std::tanh(driven);
+                break;
+
+            case DistortionType::HardClip: {
+                float threshold = 1.0f / (1.0f + distAmount * 9.0f);
+                wet = std::clamp(driven, -threshold, threshold);
+                break;
+            }
+
+            case DistortionType::Foldback: {
+                float threshold = 1.0f + distAmount * 3.0f;
+                wet = driven;
+                while (wet > threshold || wet < -threshold) {
+                    if (wet > threshold)
+                        wet = 2.0f * threshold - wet;
+                    else if (wet < -threshold)
+                        wet = -2.0f * threshold - wet;
+                    else
+                        break;
+                }
+                if (threshold > 0.0f)
+                    wet /= threshold;
+                break;
+            }
+
+            case DistortionType::Overdrive: {
+                float t = driven;
+                if (t > 1.0f) t = 1.0f;
+                else if (t < -1.0f) t = -1.0f;
+                wet = t * (1.5f - 0.5f * t * t);
+                break;
+            }
+
+            default:
+                wet = driven;
+                break;
+        }
+
+        if (distAmount < 0.001f)
+            return input;
+
+        return input + (wet - input) * dryWet;
+    }
+
+private:
+    DistortionType distType = DistortionType::SoftClip;
+    float distAmount = 0.0f;
+    float dryWet = 0.0f;
+};