Ensure 3D sources are spatialized

Standard OpenAL does not spatialize non-mono sounds, although the game has some
stereo sounds meant to play in 3D. The desired behavior can be achieved with
the AL_SOFT_source_spatialize extension.

apps/openmw/mwsound/openal_output.cpp

@@ -622,6 +622,7 @@ void OpenAL_Output::init(const std::string &devname)
     }
 
     ALC.EXT_EFX = !!alcIsExtensionPresent(mDevice, "ALC_EXT_EFX");
+    AL.SOFT_source_spatialize = !!alIsExtensionPresent("AL_SOFT_source_spatialize");
 
     alDistanceModel(AL_INVERSE_DISTANCE_CLAMPED);
     throwALerror();
@@ -972,6 +973,8 @@ void OpenAL_Output::initCommon2D(ALuint source, const osg::Vec3f &pos, ALfloat g
     alSourcef(source, AL_ROLLOFF_FACTOR, 0.0f);
     alSourcei(source, AL_SOURCE_RELATIVE, AL_TRUE);
     alSourcei(source, AL_LOOPING, loop ? AL_TRUE : AL_FALSE);
+    if(AL.SOFT_source_spatialize)
+        alSourcei(source, AL_SOURCE_SPATIALIZE_SOFT, AL_FALSE);
 
     if(useenv)
     {
@@ -1009,6 +1012,8 @@ void OpenAL_Output::initCommon3D(ALuint source, const osg::Vec3f &pos, ALfloat m
     alSourcef(source, AL_ROLLOFF_FACTOR, 1.0f);
     alSourcei(source, AL_SOURCE_RELATIVE, AL_FALSE);
     alSourcei(source, AL_LOOPING, loop ? AL_TRUE : AL_FALSE);
+    if(AL.SOFT_source_spatialize)
+        alSourcei(source, AL_SOURCE_SPATIALIZE_SOFT, AL_TRUE);
 
     if((pos - mListenerPos).length2() > maxdist*maxdist)
         gain = 0.0f;

apps/openmw/mwsound/openal_output.hpp

@@ -26,6 +26,9 @@ namespace MWSound
         struct {
             int EXT_EFX : 1;
         } ALC;
+        struct {
+            int SOFT_source_spatialize : 1;
+        } AL;
 
         typedef std::deque<ALuint> IDDq;
         IDDq mFreeSources;