Wwise SDK 2021.1.14

A typical condition is having a game object that becomes either obstructed by another object (such as a wall or beam), or occluded in a room where the listener can only hear a few sounds leaking through the walls. Auxiliary sends can represent the reflections of the signal.

The following diagrams illustrate examples of occlusion and obstruction.

Example of an Obstruction

Obstruction can be modeled by applying a volume control and/or a Low Pass Filter (LPF) affecting only the direct path of the signal. The auxiliary send reflections are unaffected.

Example of an Occlusion

Occlusion can be modeled by applying a volume control and/or a LPF affecting both the direct path and the auxiliary send reflections of the signal.

Note: Obstructions and occlusions can happen simultaneously and are modeled with the direct path being affected by both the obstruction and occlusion value. However, the reflection path is affected by the occlusion value only.

Here is a diagram of the obstruction/occlusion processing pipeline inside the sound engine:

Obstruction/Occlusion Processing Pipeline

Setting Obstruction and Occlusion

The game engine is responsible for determining the obstruction and occlusion values, which it does using the position of the objects and listeners in the game's geometry.

Sound designers have access to curves in the Wwise Project Settings/Curves Tab to determine how the volume and LPF will react to calculated obstruction and occlusion values.

Sound designers can also enable or disable the usage of any curve to best suit their performance and realism needs.

Customizing Obstruction and Occlusion Curves in Wwise

Using the curve of this snapshot, setting an obstruction value of 1.0f (100%) will produce a volume change of -50 dB on the source object.

For more information on customizing the project obstruction and occlusion curves with Wwise, refer to the Wwise Help.

Obstruction and Occlusion can also be disabled, enabled, and set per sound with the help of the Obstruction and Occlusion curves of the Attenuation ShareSet. For more information, refer to the Applying Attenuation section of the Wwise Help.

Game designers must calculate the obstruction and occlusion for each game object affecting each listener and pass down the values to the sound engine using the following call:

AK::SoundEngine::SetObjectObstructionAndOcclusion()

Caution: Obstruction and Occlusion levels must always be a value between 0.0f and 1.0f.

When multiple listeners are enabled for a game object, the sound engine determines the minimum LPF value and maximum volume value that should be heard for all listeners; it then uses that value to compute the resulting obstruction/occlusion.

Example: Setting Obstruction and Occlusion

#define MAIN_LISTENER        0
 
// game loop

while( TRUE )
{
    (...)
 
    for( int iGameObject = 0; iGameObject < nbObjects; iGameObject++ )
    {
        AkReal32 fCalculatedObs, fCalculatedOcc;
        pGeometryModule->GetObsAndOccForGameObject( iGameObject, MAIN_LISTENER, &fCalculatedObs, &fCalculatedOcc );
        AK::SoundEngine::SetObjectObstructionAndOcclusion( iGameObject, MAIN_LISTENER, fCalculatedObs, fCalculatedOcc );
    }
    
    (...)
}

See also

AkReal32

float AkReal32

32-bit floating point

Definition: AkTypes.h:70

AK::SoundEngine::SetObjectObstructionAndOcclusion

AKSOUNDENGINE_API AKRESULT SetObjectObstructionAndOcclusion(AkGameObjectID in_EmitterID, AkGameObjectID in_ListenerID, AkReal32 in_fObstructionLevel, AkReal32 in_fOcclusionLevel)

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