AudioEmitter is a helper object derived from X3DAUDIO_EMITTER used by SoundEffectInstance's / DynamicSoundEffectInstance's Apply3D method.

See AudioListener.

Initialization

The default constructor creates a point omnidirectional emitter located at 0,0,0 facing +z and an up vector of +y for a mono source.

CurveDistanceScaler and DopplerScaler are set to 1 by default. InnerRadius is set to 0, and InnerRadiusAngle is set to X3DAUDIO_PI/4.0 (45 degrees).

Helpers

In addition to setting the members of X3DAUDIO_EMITTER directly, these helper functions are provided:

• SetPosition (FXVMECTOR) or (XMFLOAT3)

Sets the Position of the emitter.

• SetVelocity (FXMVECTOR) or (XMFLOAT3)

Sets the Velocity of the emitter.

• SetOrientation (FXMVECTOR forward, FXVMECTOR up) or (XMFLOAT3 forward, XMFLOAT3 up)
• SetOrientationFromQuaternion ( FXMVECTOR )

Sets the OrientFront/OrientTop of the emitter.

• Update ( FXMVECTOR newPos, XMVECTOR upDir, float dt )

Computes a direction and velocity for the emitter based on the existing Position and the newPos, updating the OrientFront/OrientTop to match, and then setting the Position to the newPos. If dt is 0, the update is skipped.

Multi-channel 3D Audio

X3DAudio does support multi-channel sound sources for 3D audio (i.e. stereo, quad, etc.). The default constructor for AudioEmitter sets the source up for mono (i.e. single-channel), so to use multi-channel sources, you should set the ChannelCount member to match the number of channels in your source, and adjust ChannelRadius and the EmitterAzimuths array as desired..

AudioEmitter includes a EmitterAzimuths array which is pointed to by pChannelAzimuths and defaults to all 0. This is because pChannelAzimuths cannot be a nullptr for multi-channel sound emitters.

Directional Emitters

AudioEmitter defaults to an omnidirectional emitter. To create a sound-cone, set the pCone member to point to a X3DAUDIO_CONE structure. The pointer must point to valid memory at the time Apply3D is called.

Custom distance curves

AudioEmitter constructor sets pVolumeCurve, pLFECurve, pLPFDirectCurve, pLPFReverbCurve, and pReverbCurve to nullptr which uses XAudio2 default curves. Any custom curve definitions must have a pointer to valid memory at the time Apply3D is called.

Further reading

http://msdn.microsoft.com/en-us/library/windows/desktop/microsoft.directx_sdk.x3daudio.x3daudio_emitter.aspx