Gaussian Spread

Scripts/Utils/RandomStuff.cs

@@ -0,0 +1,40 @@
+using System;
+using Godot;
+
+namespace Cirno.Scripts.Utils;
+
+public static class RandomStuff
+{
+    public static double GaussianRandom(double mean = 0.0, double stdDev = 1.0)
+    {
+        // Box-Muller transform
+        float u1 = GD.Randf();
+        float u2 = GD.Randf();
+
+        // Ensure u1 is strictly > 0
+        while (u1 <= 0f)
+            u1 = GD.Randf();
+
+        float randStdNormal = Mathf.Sqrt(-2f * Mathf.Log(u1)) * Mathf.Sin(2f * Mathf.Pi * u2);
+        return mean + stdDev * randStdNormal;
+    }
+    
+    public static float GaussianClamped(float mean, float stdDev, float min, float max)
+    {
+        float value;
+        do
+        {
+            float u1 = GD.Randf();
+            float u2 = GD.Randf();
+
+            // Ensure u1 > 0 to avoid log(0)
+            while (u1 <= 0f) u1 = GD.Randf();
+
+            float randStdNormal = Mathf.Sqrt(-2f * Mathf.Log(u1)) * Mathf.Sin(2f * Mathf.Pi * u2);
+            value = mean + stdDev * randStdNormal;
+        }
+        while (value < min || value > max); // reject out-of-bounds values
+
+        return value;
+    }
+}

Scripts/Utils/RandomStuff.cs.uid

@@ -0,0 +1 @@
+uid://tkwp2w30xi32

Scripts/Weapon.cs

@@ -4,6 +4,7 @@ using System.Diagnostics;
 using Cirno.Scripts;
 using Cirno.Scripts.Components;
 using Cirno.Scripts.Resources;
+using Cirno.Scripts.Utils;
 
 public partial class Weapon : Node2D
 {
@@ -123,6 +124,18 @@ public partial class Weapon : Node2D
 			// Calculate angle offset for this bullet
 			float spreadOffset = -halfSpread + (spreadStep * i);
 
+			// Add random spread
+			if (WeaponData.RandomSpread > 0)
+			{
+				// Gaussian with mean = 0, stddev = WeaponData.RandomSpread
+				spreadOffset += RandomStuff.GaussianClamped(
+					mean: 0f,
+					stdDev: WeaponData.RandomSpread, // tuning knob
+					min: -halfSpread,
+					max: halfSpread
+				);
+			}
+			
 			// Rotate the ShootDirection by the spread angle
 			Vector2 spreadDirection = ShootDirection.Rotated(Mathf.DegToRad(spreadOffset));