Fix source sends' initial HF absorption and decay calculation

The HF absorption is applied given the source distance, as relative to the
source's immediate environment, with additional absorption being applied given
the room/reverb environment. This does double up the amount of absorption
compared to the dry path, but it can be assumed the initial reflections travel
a longer distance.

3 files changed, 17 insertions, 23 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index 7bf6f2ff..d7a8a89b 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -348,16 +348,16 @@ static ALboolean CalcEffectSlotParams(ALeffectslot *slot, ALCdevice *device)
         slot->Params.RoomRolloff = props->Props.Reverb.RoomRolloffFactor;
         slot->Params.DecayTime = props->Props.Reverb.DecayTime;
         slot->Params.DecayHFRatio = props->Props.Reverb.DecayHFRatio;
-        slot->Params.AirAbsorptionGainHF = props->Props.Reverb.AirAbsorptionGainHF;
         slot->Params.DecayHFLimit = props->Props.Reverb.DecayHFLimit;
+        slot->Params.AirAbsorptionGainHF = props->Props.Reverb.AirAbsorptionGainHF;
     }
     else
     {
         slot->Params.RoomRolloff = 0.0f;
         slot->Params.DecayTime = 0.0f;
         slot->Params.DecayHFRatio = 0.0f;
-        slot->Params.AirAbsorptionGainHF = 1.0f;
         slot->Params.DecayHFLimit = AL_FALSE;
+        slot->Params.AirAbsorptionGainHF = 1.0f;
     }
 
     /* Swap effect states. No need to play with the ref counts since they keep
@@ -1079,7 +1079,6 @@ static void CalcAttnSourceParams(ALvoice *voice, const struct ALvoiceProps *prop
     const ALsizei NumSends = Device->NumAuxSends;
     aluVector Position, Velocity, Direction, SourceToListener;
     ALfloat Distance, ClampedDist, DopplerFactor;
-    ALfloat RoomAirAbsorption[MAX_SENDS];
     ALeffectslot *SendSlots[MAX_SENDS];
     ALfloat RoomRolloff[MAX_SENDS];
     ALfloat DecayDistance[MAX_SENDS];
@@ -1108,20 +1107,20 @@ static void CalcAttnSourceParams(ALvoice *voice, const struct ALvoiceProps *prop
             RoomRolloff[i] = 0.0f;
             DecayDistance[i] = 0.0f;
             DecayHFDistance[i] = 0.0f;
-            RoomAirAbsorption[i] = 1.0f;
         }
         else if(SendSlots[i]->Params.AuxSendAuto)
         {
             RoomRolloff[i] = SendSlots[i]->Params.RoomRolloff + props->RoomRolloffFactor;
             DecayDistance[i] = SendSlots[i]->Params.DecayTime * SPEEDOFSOUNDMETRESPERSEC;
             DecayHFDistance[i] = DecayDistance[i] * SendSlots[i]->Params.DecayHFRatio;
-            RoomAirAbsorption[i] = SendSlots[i]->Params.AirAbsorptionGainHF;
-            if(SendSlots[i]->Params.DecayHFLimit && RoomAirAbsorption[i] < 1.0f)
+            if(SendSlots[i]->Params.DecayHFLimit)
             {
-                ALfloat limitRatio = log10f(REVERB_DECAY_GAIN) /
-                                     (log10f(RoomAirAbsorption[i]) * DecayDistance[i]);
-                limitRatio = minf(limitRatio, SendSlots[i]->Params.DecayHFRatio);
-                DecayHFDistance[i] = minf(DecayHFDistance[i], limitRatio*DecayDistance[i]);
+                ALfloat airAbsorption = SendSlots[i]->Params.AirAbsorptionGainHF;
+                if(airAbsorption < 1.0f)
+                {
+                    ALfloat limitRatio = log10f(REVERB_DECAY_GAIN) / log10f(airAbsorption);
+                    DecayHFDistance[i] = minf(limitRatio, DecayHFDistance[i]);
+                }
             }
         }
         else
@@ -1131,7 +1130,6 @@ static void CalcAttnSourceParams(ALvoice *voice, const struct ALvoiceProps *prop
             RoomRolloff[i] = props->RolloffFactor;
             DecayDistance[i] = 0.0f;
             DecayHFDistance[i] = 0.0f;
-            RoomAirAbsorption[i] = AIRABSORBGAINHF;
         }
 
         if(!SendSlots[i])
@@ -1249,24 +1247,20 @@ static void CalcAttnSourceParams(ALvoice *voice, const struct ALvoiceProps *prop
     }
 
     /* Distance-based air absorption */
-    if(ClampedDist > props->RefDistance)
+    if(ClampedDist > props->RefDistance && props->RolloffFactor > 0.0f)
     {
-        ALfloat meters_base = (ClampedDist-props->RefDistance) * Listener->Params.MetersPerUnit;
+        ALfloat meters_base = (ClampedDist-props->RefDistance) * props->RolloffFactor *
+                              Listener->Params.MetersPerUnit;
         if(props->AirAbsorptionFactor > 0.0f)
         {
-            ALfloat absorb = props->AirAbsorptionFactor * meters_base;
-            DryGainHF *= powf(AIRABSORBGAINHF, absorb*props->RolloffFactor);
+            ALfloat hfattn = powf(AIRABSORBGAINHF, meters_base * props->AirAbsorptionFactor);
+            DryGainHF *= hfattn;
             for(i = 0;i < NumSends;i++)
-            {
-                if(RoomRolloff[i] > 0.0f)
-                    WetGainHF[i] *= powf(AIRABSORBGAINHF, absorb*RoomRolloff[i]);
-            }
+                WetGainHF[i] *= hfattn;
         }
 
         if(props->WetGainAuto)
         {
-            meters_base *= props->RolloffFactor;
-
             /* Apply a decay-time transformation to the wet path, based on the
              * source distance in meters. The initial decay of the reverb
              * effect is calculated and applied to the wet path.
diff --git a/OpenAL32/Include/alAuxEffectSlot.h b/OpenAL32/Include/alAuxEffectSlot.h
index 7126f8f5..5be9ae7a 100644
--- a/OpenAL32/Include/alAuxEffectSlot.h
+++ b/OpenAL32/Include/alAuxEffectSlot.h
@@ -122,8 +122,8 @@ typedef struct ALeffectslot {
         ALfloat RoomRolloff; /* Added to the source's room rolloff, not multiplied. */
         ALfloat DecayTime;
         ALfloat DecayHFRatio;
-        ALfloat AirAbsorptionGainHF;
         ALboolean DecayHFLimit;
+        ALfloat AirAbsorptionGainHF;
     } Params;
 
     /* Self ID */
diff --git a/OpenAL32/alAuxEffectSlot.c b/OpenAL32/alAuxEffectSlot.c
index 8a990584..cd2c1e09 100644
--- a/OpenAL32/alAuxEffectSlot.c
+++ b/OpenAL32/alAuxEffectSlot.c
@@ -616,8 +616,8 @@ ALenum InitEffectSlot(ALeffectslot *slot)
     slot->Params.RoomRolloff = 0.0f;
     slot->Params.DecayTime = 0.0f;
     slot->Params.DecayHFRatio = 0.0f;
-    slot->Params.AirAbsorptionGainHF = 1.0f;
     slot->Params.DecayHFLimit = AL_FALSE;
+    slot->Params.AirAbsorptionGainHF = 1.0f;
 
     return AL_NO_ERROR;
 }