Add real-time note detection and NOTEDROP visualization

Implemented musical note detection in AudioAnalyzer, exposing dominant note and strength in AudioFeatures. Updated HUD to display detected note. Added "NOTEDROP" fractal preset that animates detected notes as colored glyphs. Extended bitmap font to support sharps. Increased fractal preset count and adjusted HUD layout.

FractalVisualizer/Audio/AudioAnalyzer.cs

@@ -168,6 +168,8 @@ public sealed class AudioAnalyzer : IDisposable
         float bassEnergy = 0f;
         float midEnergy = 0f;
         float highEnergy = 0f;
+        float dominantMagnitude = 0f;
+        float dominantFrequency = 0f;
 
         for (int bin = 1; bin < half; bin++)
         {
@@ -195,6 +197,12 @@ public sealed class AudioAnalyzer : IDisposable
             {
                 highEnergy += magnitude;
             }
+
+            if (frequency >= 80f && frequency <= 2000f && magnitude > dominantMagnitude)
+            {
+                dominantMagnitude = magnitude;
+                dominantFrequency = frequency;
+            }
         }
 
         float[] spectrum = new float[_spectrumBins];
@@ -248,6 +256,9 @@ public sealed class AudioAnalyzer : IDisposable
         float bpmInstant = CalculateBpm();
         _smoothedBpm = Smooth(_smoothedBpm, bpmInstant, 0.18f, 0.04f);
 
+        int noteIndex = GetNoteIndexFromFrequency(dominantFrequency);
+        float dominantStrength = Clamp01(dominantMagnitude * 0.02f);
+
         AudioFeatures features = new()
         {
             Level = _smoothedLevel,
@@ -256,6 +267,9 @@ public sealed class AudioAnalyzer : IDisposable
             High = _smoothedHigh,
             Beat = _smoothedBeat,
             Bpm = _smoothedBpm,
+            DominantFrequencyHz = dominantFrequency,
+            DetectedNoteIndex = noteIndex,
+            DetectedNoteStrength = dominantStrength,
             Spectrum = spectrum,
             TimeSeconds = now
         };
@@ -319,6 +333,38 @@ public sealed class AudioAnalyzer : IDisposable
         return Math.Clamp(bpm, 40f, 220f);
     }
 
+    private static int GetNoteIndexFromFrequency(float frequencyHz)
+    {
+        if (frequencyHz <= 0f)
+        {
+            return -1;
+        }
+
+        float midi = 69f + (12f * MathF.Log2(frequencyHz / 440f));
+        int note = ((int)MathF.Round(midi)) % 12;
+        if (note < 0)
+        {
+            note += 12;
+        }
+
+        return note;
+    }
+
+    private static float Clamp01(float value)
+    {
+        if (value < 0f)
+        {
+            return 0f;
+        }
+
+        if (value > 1f)
+        {
+            return 1f;
+        }
+
+        return value;
+    }
+
     private void ThrowIfDisposed()
     {
         if (_disposed)

FractalVisualizer/Game1.cs

@@ -145,7 +145,7 @@ public class Game1 : Game
 
         if (IsPressed(keyboard, Keys.Right))
         {
-            _fractalPresetIndex = Math.Min(19, _fractalPresetIndex + 1);
+            _fractalPresetIndex = Math.Min(20, _fractalPresetIndex + 1);
         }
 
         if (IsPressed(keyboard, Keys.M))
@@ -194,10 +194,11 @@ public class Game1 : Game
             _hudFont.DrawText(_spriteBatch, _pixel, "HIGH  " + _latestFeatures.High.ToString("0.000"), 12, 110, 2, Color.White);
             _hudFont.DrawText(_spriteBatch, _pixel, "BEAT  " + _latestFeatures.Beat.ToString("0.000"), 12, 130, 2, Color.White);
             _hudFont.DrawText(_spriteBatch, _pixel, "BPM   " + _latestFeatures.Bpm.ToString("0.0"), 12, 150, 2, Color.White);
-            _hudFont.DrawText(_spriteBatch, _pixel, "PAUSED " + (_isPaused ? "YES" : "NO"), 12, 170, 2, Color.White);
+            _hudFont.DrawText(_spriteBatch, _pixel, "NOTE  " + GetDetectedNoteName(_latestFeatures.DetectedNoteIndex), 12, 170, 2, Color.White);
-            _hudFont.DrawText(_spriteBatch, _pixel, "FPS   " + _fps, 12, 190, 2, Color.White);
+            _hudFont.DrawText(_spriteBatch, _pixel, "PAUSED " + (_isPaused ? "YES" : "NO"), 12, 190, 2, Color.White);
-            _hudFont.DrawText(_spriteBatch, _pixel, "QUALITY " + _renderQuality + "  1 2 3", 12, 210, 2, Color.White);
+            _hudFont.DrawText(_spriteBatch, _pixel, "FPS   " + _fps, 12, 210, 2, Color.White);
-            _hudFont.DrawText(_spriteBatch, _pixel, "F OR F11 FULLSCREEN  R RESIZE", 12, 230, 2, Color.White);
+            _hudFont.DrawText(_spriteBatch, _pixel, "QUALITY " + _renderQuality + "  1 2 3", 12, 230, 2, Color.White);
+            _hudFont.DrawText(_spriteBatch, _pixel, "F OR F11 FULLSCREEN  R RESIZE", 12, 250, 2, Color.White);
             _spriteBatch.End();
         }
 
@@ -247,10 +248,31 @@ public class Game1 : Game
             17 => "MOSAIC",
             18 => "RIBBON",
             19 => "GRAINBARS",
+            20 => "NOTEDROP",
             _ => "JULIA"
         };
     }
 
+    private static string GetDetectedNoteName(int noteIndex)
+    {
+        return noteIndex switch
+        {
+            0 => "C",
+            1 => "C#",
+            2 => "D",
+            3 => "D#",
+            4 => "E",
+            5 => "F",
+            6 => "F#",
+            7 => "G",
+            8 => "G#",
+            9 => "A",
+            10 => "A#",
+            11 => "B",
+            _ => "-"
+        };
+    }
+
     private void ToggleFullScreen()
     {
         _graphics.ToggleFullScreen();

FractalVisualizer/Models/AudioFeatures.cs

@@ -8,6 +8,9 @@ public struct AudioFeatures
     public float High;
     public float Beat;
     public float Bpm;
+    public float DominantFrequencyHz;
+    public int DetectedNoteIndex;
+    public float DetectedNoteStrength;
     public float[] Spectrum;
     public float TimeSeconds;
 

FractalVisualizer/Rendering/FractalRenderer.cs

@@ -18,11 +18,28 @@ public sealed class FractalRenderer : IDisposable
     private Color[] _postBuffer;
     private Color[] _previousFrame;
     private readonly List<NoteParticle> _notes = [];
+    private readonly List<DetectedNoteParticle> _detectedNotes = [];
     private readonly List<FireworkRocket> _fireworkRockets = [];
     private readonly List<FireworkSpark> _fireworkSparks = [];
     private readonly Random _rng = new();
+    private static readonly string[] NoteNames =
+    [
+        "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"
+    ];
+    private static readonly Dictionary<char, string[]> NoteGlyphs = new()
+    {
+        ['A'] = ["01110", "10001", "10001", "11111", "10001", "10001", "10001"],
+        ['B'] = ["11110", "10001", "10001", "11110", "10001", "10001", "11110"],
+        ['C'] = ["01111", "10000", "10000", "10000", "10000", "10000", "01111"],
+        ['D'] = ["11110", "10001", "10001", "10001", "10001", "10001", "11110"],
+        ['E'] = ["11111", "10000", "10000", "11110", "10000", "10000", "11111"],
+        ['F'] = ["11111", "10000", "10000", "11110", "10000", "10000", "10000"],
+        ['G'] = ["01111", "10000", "10000", "10111", "10001", "10001", "01111"],
+        ['#'] = ["01010", "11111", "01010", "01010", "11111", "01010", "00000"]
+    };
 
     private float _noteSpawnAccumulator;
+    private float _detectedNoteAccumulator;
     private float _fireworkSpawnAccumulator;
     private float _runtimePerformanceScale = 1f;
     private RenderQuality _quality = RenderQuality.Medium;
@@ -114,9 +131,11 @@ public sealed class FractalRenderer : IDisposable
         _postBuffer = new Color[_internalWidth * _internalHeight];
         _previousFrame = new Color[_internalWidth * _internalHeight];
         _notes.Clear();
+        _detectedNotes.Clear();
         _fireworkRockets.Clear();
         _fireworkSparks.Clear();
         _noteSpawnAccumulator = 0f;
+        _detectedNoteAccumulator = 0f;
         _fireworkSpawnAccumulator = 0f;
     }
 
@@ -201,6 +220,9 @@ public sealed class FractalRenderer : IDisposable
             case 19:
                 RenderGrainBars(features, timeSeconds);
                 break;
+            case 20:
+                RenderDetectedNotes(features, timeSeconds);
+                break;
             default:
                 RenderJulia(features, timeSeconds);
                 break;
@@ -1158,6 +1180,116 @@ public sealed class FractalRenderer : IDisposable
         }
     }
 
+    private void RenderDetectedNotes(AudioFeatures features, float timeSeconds)
+    {
+        for (int y = 0; y < _internalHeight; y++)
+        {
+            float t = y / (float)(_internalHeight - 1);
+            Color bg = new(0.02f, 0.02f + 0.04f * (1f - t), 0.05f + 0.10f * (1f - t), 1f);
+            int row = y * _internalWidth;
+            for (int x = 0; x < _internalWidth; x++)
+            {
+                _pixelBuffer[row + x] = bg;
+            }
+        }
+
+        float spawnRate = features.DetectedNoteStrength * (0.3f + Clamp01(features.Beat) * 1.3f);
+        _detectedNoteAccumulator += spawnRate * _runtimePerformanceScale;
+        while (_detectedNoteAccumulator >= 1f)
+        {
+            SpawnDetectedNote(features);
+            _detectedNoteAccumulator -= 1f;
+        }
+
+        for (int i = _detectedNotes.Count - 1; i >= 0; i--)
+        {
+            DetectedNoteParticle p = _detectedNotes[i];
+            p.X += p.Vx;
+            p.Y += p.Vy;
+            p.Vy -= 0.00002f;
+            p.Life -= 0.008f + (1f - features.DetectedNoteStrength) * 0.006f;
+
+            if (p.Life <= 0f || p.X < -0.2f || p.X > 1.2f || p.Y < -0.2f)
+            {
+                _detectedNotes.RemoveAt(i);
+                continue;
+            }
+
+            _detectedNotes[i] = p;
+            DrawDetectedNoteText(p);
+        }
+    }
+
+    private void SpawnDetectedNote(AudioFeatures features)
+    {
+        if (features.DetectedNoteIndex < 0 || features.DetectedNoteIndex > 11)
+        {
+            return;
+        }
+
+        if (_detectedNotes.Count >= ScaleCount(96, 20))
+        {
+            return;
+        }
+
+        string text = NoteNames[features.DetectedNoteIndex];
+        float x = 0.1f + (float)_rng.NextDouble() * 0.8f;
+        float y = 0.25f + (float)_rng.NextDouble() * 0.65f;
+        float vx = ((float)_rng.NextDouble() - 0.5f) * 0.0022f;
+        float vy = -(0.0014f + (float)_rng.NextDouble() * 0.0025f);
+        float scale = 1.2f + (float)_rng.NextDouble() * (1.8f + features.DetectedNoteStrength * 1.6f);
+        float hue = features.DetectedNoteIndex / 12f;
+        Vector3 color = new(
+            0.5f + 0.5f * MathF.Sin(hue * MathF.Tau),
+            0.5f + 0.5f * MathF.Sin(hue * MathF.Tau + 2.09f),
+            0.5f + 0.5f * MathF.Sin(hue * MathF.Tau + 4.18f));
+
+        _detectedNotes.Add(new DetectedNoteParticle
+        {
+            X = x,
+            Y = y,
+            Vx = vx,
+            Vy = vy,
+            Life = 1f,
+            Scale = scale,
+            Text = text,
+            Color = color
+        });
+    }
+
+    private void DrawDetectedNoteText(DetectedNoteParticle p)
+    {
+        int px = (int)(p.X * _internalWidth);
+        int py = (int)(p.Y * _internalHeight);
+        int scale = Math.Max(1, (int)MathF.Round(p.Scale));
+        for (int i = 0; i < p.Text.Length; i++)
+        {
+            DrawGlyph(p.Text[i], px + i * (6 * scale), py, scale, p.Color, p.Life);
+        }
+    }
+
+    private void DrawGlyph(char c, int x, int y, int scale, Vector3 color, float alpha)
+    {
+        if (!NoteGlyphs.TryGetValue(c, out string[]? glyph))
+        {
+            return;
+        }
+
+        for (int row = 0; row < glyph.Length; row++)
+        {
+            string line = glyph[row];
+            for (int col = 0; col < line.Length; col++)
+            {
+                if (line[col] != '1')
+                {
+                    continue;
+                }
+
+                DrawRect(x + col * scale, y + row * scale, scale, scale, color, alpha);
+            }
+        }
+    }
+
     private void SpawnFireworkRocket(float intensity)
     {
         if (_fireworkRockets.Count >= ScaleCount(42, 12))
@@ -1478,6 +1610,18 @@ public sealed class FractalRenderer : IDisposable
         public bool HasFlag;
     }
 
+    private struct DetectedNoteParticle
+    {
+        public float X;
+        public float Y;
+        public float Vx;
+        public float Vy;
+        public float Life;
+        public float Scale;
+        public string Text;
+        public Vector3 Color;
+    }
+
     private struct FireworkRocket
     {
         public float X;

FractalVisualizer/UI/HudBitmapFont.cs

@@ -44,6 +44,7 @@ public sealed class HudBitmapFont
         ['7'] = ["11111", "00001", "00010", "00100", "01000", "01000", "01000"],
         ['8'] = ["01110", "10001", "10001", "01110", "10001", "10001", "01110"],
         ['9'] = ["01110", "10001", "10001", "01111", "00001", "00001", "01110"],
+        ['#'] = ["01010", "11111", "01010", "01010", "11111", "01010", "00000"],
         ['.'] = ["00000", "00000", "00000", "00000", "00000", "00110", "00110"],
         ['-'] = ["00000", "00000", "00000", "01110", "00000", "00000", "00000"],
         [':'] = ["00000", "00110", "00110", "00000", "00110", "00110", "00000"],