From 39066900773e7857faf2d02e7ed51b71d219d97d Mon Sep 17 00:00:00 2001
From: godosa <godosa@godosa.eu>
Date: Tue, 6 Oct 2026 23:39:36 +0200
Subject: godosa-engine: initial public history

---
 src/Godosa.Audio/OpenAlAudio.Reverb.cs | 83 ++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 src/Godosa.Audio/OpenAlAudio.Reverb.cs

(limited to 'src/Godosa.Audio/OpenAlAudio.Reverb.cs')

diff --git a/src/Godosa.Audio/OpenAlAudio.Reverb.cs b/src/Godosa.Audio/OpenAlAudio.Reverb.cs
new file mode 100644
index 0000000..b93e74a
--- /dev/null
+++ b/src/Godosa.Audio/OpenAlAudio.Reverb.cs
@@ -0,0 +1,83 @@
+using Silk.NET.OpenAL.Extensions.Creative;
+
+namespace Godosa.Audio;
+
+/// <summary>One EFX reverb for the region (audio spec §2): positioned sources send to it, 2D
+/// ones (beds, music, interface) don't. Air absorption dulls distant sounds.</summary>
+public sealed unsafe partial class OpenAlAudio
+{
+    private EffectExtension? _efx;
+    private uint _effect, _effectSlot;
+    private ReverbPreset? _reverbApplied;
+    private ReverbPreset? _reverbWanted;
+    private bool _reverbInitialised;
+
+    /// <summary>The current region's reverb, or null for none (UI thread).</summary>
+    public ReverbPreset? Reverb
+    {
+        set { lock (_poseLock) _reverbWanted = value; }
+    }
+
+    private void InitReverb()
+    {
+        if (!_al!.TryGetExtension(out _efx)) _efx = null;
+        if (_efx is null)
+        {
+            if (EngineDebug.Audio) EngineDebug.Write("audio", "no EFX: no reverb");
+            return;
+        }
+        _effect = _efx.GenEffects(1)[0];
+        _efx.SetEffectProperty(_effect, EffectInteger.EffectType, (int)EffectType.Reverb);
+        _effectSlot = _efx.GenAuxiliaryEffectSlots(1)[0];
+        _reverbApplied = null;
+        _reverbInitialised = false;
+    }
+
+    private void UpdateReverb()
+    {
+        if (_efx is null) return;
+        ReverbPreset? wanted;
+        lock (_poseLock) wanted = _reverbWanted;
+        if (_reverbInitialised && _reverbApplied == wanted) return;
+        _reverbInitialised = true;
+        _reverbApplied = wanted;
+        if (wanted is not { } p)
+        {
+            // No effect in the slot: sends to it are dropped and the mixer runs no reverb.
+            _efx.SetAuxiliaryEffectSlotProperty(_effectSlot, EffectSlotInteger.Effect, 0);
+            if (EngineDebug.Audio) EngineDebug.Write("audio", "reverb off");
+            return;
+        }
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbDensity, p.Density);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbDiffusion, p.Diffusion);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbGain, p.Gain);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbGainHF, p.GainHF);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbDecayTime, p.DecayTime);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbDecayHFRatio, p.DecayHFRatio);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbReflectionsGain, p.ReflectionsGain);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbReflectionsDelay, p.ReflectionsDelay);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbLateReverbGain, p.LateReverbGain);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbLateReverbDelay, p.LateReverbDelay);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbAirAbsorptionGainHF, p.AirAbsorptionGainHF);
+        _efx.SetEffectProperty(_effect, EffectFloat.ReverbRoomRolloffFactor, p.RoomRolloffFactor);
+        _efx.SetEffectProperty(_effect, EffectInteger.ReverbDecayHFLimit, p.DecayHFLimit ? 1 : 0);
+        _efx.SetAuxiliaryEffectSlotProperty(_effectSlot, EffectSlotInteger.Effect, (int)_effect); // re-attach applies the change
+        if (EngineDebug.Audio) EngineDebug.Write("audio", $"reverb {(p == ReverbPreset.Forest ? "forest" : p == ReverbPreset.Cave ? "cave" : "plain")}");
+    }
+
+    private void SendToReverb(uint source, bool positioned)
+    {
+        if (_efx is null) return;
+        _efx.SetSourceProperty(source, EFXSourceInteger3.AuxiliarySendFilter, positioned ? (int)_effectSlot : 0, 0, 0);
+        _efx.SetSourceProperty(source, EFXSourceFloat.AirAbsorptionFactor, positioned ? 1f : 0f);
+    }
+
+    private void ReleaseReverb()
+    {
+        if (_efx is null) return;
+        _efx.SetAuxiliaryEffectSlotProperty(_effectSlot, EffectSlotInteger.Effect, 0);
+        _efx.DeleteAuxiliaryEffectSlot(_effectSlot);
+        _efx.DeleteEffect(_effect);
+        _efx = null;
+    }
+}
-- 
cgit