Adds a semitone shifting AudioHelper (#2608)

* Add semitone audio helper

* use semitone audio helper on bike horn

* prettify

* clamp this instead

* Expose these to viewvars

Content.Server/GameObjects/Components/Sound/EmitSoundOnUseComponent.cs

@@ -5,6 +5,7 @@ using Robust.Shared.Audio;
 using Robust.Shared.GameObjects;
 using Robust.Shared.GameObjects.Systems;
 using Robust.Shared.Serialization;
+using Robust.Shared.ViewVariables;
 
 namespace Content.Server.GameObjects.Components.Sound
 {
@@ -18,14 +19,16 @@ namespace Content.Server.GameObjects.Components.Sound
         ///
         public override string Name => "EmitSoundOnUse";
 
-        public string _soundName;
+        [ViewVariables(VVAccess.ReadWrite)] public string _soundName;
-        public float _pitchVariation;
+        [ViewVariables(VVAccess.ReadWrite)] public float _pitchVariation;
+        [ViewVariables(VVAccess.ReadWrite)] public int _semitoneVariation;
 
         public override void ExposeData(ObjectSerializer serializer)
         {
             base.ExposeData(serializer);
             serializer.DataField(ref _soundName, "sound", string.Empty);
             serializer.DataField(ref _pitchVariation, "variation", 0.0f);
+            serializer.DataField(ref _semitoneVariation, "semitoneVariation", 0);
         }
 
         bool IUse.UseEntity(UseEntityEventArgs eventArgs)
@@ -37,6 +40,11 @@ namespace Content.Server.GameObjects.Components.Sound
                     EntitySystem.Get<AudioSystem>().PlayFromEntity(_soundName, Owner, AudioHelpers.WithVariation(_pitchVariation).WithVolume(-2f));
                     return true;
                 }
+                if (_semitoneVariation > 0)
+                {
+                    EntitySystem.Get<AudioSystem>().PlayFromEntity(_soundName, Owner, AudioHelpers.WithSemitoneVariation(_semitoneVariation).WithVolume(-2f));
+                    return true;
+                }
                 EntitySystem.Get<AudioSystem>().PlayFromEntity(_soundName, Owner, AudioParams.Default.WithVolume(-2f));
                 return true;
             }

Content.Shared/Audio/AudioHelpers.cs

@@ -1,6 +1,8 @@
+using System;
 using Robust.Shared.Audio;
 using Robust.Shared.Interfaces.Random;
 using Robust.Shared.IoC;
+using Robust.Shared.Maths;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Random;
 
@@ -16,6 +18,41 @@ namespace Content.Shared.Audio
             return AudioParams.Default.WithPitchScale(scale);
         }
 
+        // Might as well just hardcode these because the audio system is limited to pitching up and down
+        // by 12 semitones anyway (ie. 0.5 to 2.0 multiplier).
+        private static readonly float[] SemitoneMultipliers =
+        {
+            0.5f, 233.08f/440f, 246.94f/440f, 261.63f/440f,
+            277.18f/440f, 293.66f/440f, 311.13f/440f, 329.63f/440f,
+            349.23f/440f, 369.99f/440f, 392.00f/440f, 415.30f/440f,
+            1.0f,
+            466.16f/440f, 493.88f/440f, 523.25f/440f, 554.37f/440f,
+            587.33f/440f, 622.25f/440f, 659.26f/440f, 698.46f/440f,
+            739.99f/440f, 783.99f/440f, 830.61f/440f, 2.0f
+        };
+
+        /// <summary>
+        /// Returns a pitch multiplier that shifts by the given number of semitones.
+        /// </summary>
+        /// <param name="shift">Number of semitones to shift, positive or negative. Clamped between -12 and 12
+        /// which correspond to a pitch multiplier of 0.5 and 2.0 respectively.</param>
+        public static AudioParams ShiftSemitone(int shift)
+        {
+            shift = MathHelper.Clamp(shift, -12, 12);
+            float pitchMult = SemitoneMultipliers[shift + 12];
+            return AudioParams.Default.WithPitchScale(pitchMult);
+        }
+
+        /// <summary>
+        /// Returns a pitch multiplier shifted by a random number of semitones within variation.
+        /// </summary>
+        /// <param name="variation">Max number of semitones to shift in either direction. Values above 12 have no effect.</param>
+        public static AudioParams WithSemitoneVariation(int variation)
+        {
+            variation = Math.Clamp(variation, 0, 12);
+            return ShiftSemitone(IoCManager.Resolve<IRobustRandom>().Next(-variation, variation));
+        }
+
         public static string GetRandomFileFromSoundCollection(string name)
         {
             var soundCollection = IoCManager.Resolve<IPrototypeManager>().Index<SoundCollectionPrototype>(name);

Resources/Prototypes/Entities/Objects/Fun/bike_horn.yml

@@ -17,7 +17,7 @@
 
   - type: EmitSoundOnUse
     sound: /Audio/Items/bikehorn.ogg
-    variation: 0.2
+    semitoneVariation: 6
 
   - type: UseDelay
     delay: 0.5