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Playing with sound spatialization


Playing sounds and musics is great, but for it to be perfectly integrated into your 2D or 3D environment, it's event better to add some spatialization. Let's have a look at some simple SFML functions for this.

The listener

Whatever the number of sounds and musics you put in your scene, they all will be listened by a single "actor" in your scene : the listener. What the listener will hear, is what will be outputed to your speakers.

SFML defines an interface for setting the listener's properties : sf::Listener. As the listener is unique in the scene, this class contains only static functions and doesn't need to be instanciated.

First, you can set the listener's position in the scene :

sf::Listener::SetPosition(10.f, 0.f, 5.f);

If you have a 2D world you can just use the same Y value everywhere, usually 0.
By default, the listener is located at the origin of the world (the point (0, 0, 0)).

Then, you can define where the listener is looking at, to set its orientation :

sf::Listener::SetTarget(15.f, 0.f, 5.f);

Here, our listener is looking along the +X axis. This means that, for example, a sound coming from (15, 0, 3) will be heard from the right speaker.
By default, the listener is looking along the -Z axis (vector (0, 0, -1)).

Finally, the listener can adjust the global volume of the scene, which would be equivalent to change the volume of all the audio sources :


The value of the volume is in the range [0, 100] ; so setting it to 50 will reduce it to half.

Note that all the listener's parameters can be read with the corresponding GetXxx functions.

Sounds and musics in your scene

There's not much more to say about sounds and musics. You can set their position in your 2D or 3D environment :

sf::Sound 3DSound;
3DSound.SetPosition(3.f, 2.f, 6.f);

By default, the position is in absolute coordinates. You can make it relative to the listener if necessary:


This has the side-effect of disabling spacialization if the position is kept to (0, 0, 0). Disabling spacialization is especially useful for sounds that are not part of the scene (GUI sounds, etc.).

You can also set the way they will be attenuated according to their distance to the listener :


The minimum distance is the distance under which the sound will be heard at its maximum volume. So, louder sounds (like explosions) should have a higher minimum distance to ensure they will be heard from far. Please note that a minimum distance of 0 (ie. the sound is in the head of the listener :) ) would lead to an incorrect value and result in a non-attenuated sound ; never use 0.
The default value for the minimum distance is 1.

The attenuation is a multiplicative factor. The more the attenuation, the less it will be heard when the sound moves away from the listener.
To get a non-attenuated sound, you can use 0. On the other hand, using a value like 100 will highly attenuate the sound, ie it wil be heard only if very close to the listener.
The default value for attenuation is 1.

Here is the exact attenuation formula, in case you need accurate values :

    MinDistance is the sound minimum distance, set with SetMinDistance
    Attenuation is the sound attenuation, set with SetAttenuation
    Distance    is the distance between the sound and the listener

    Factor = MinDistance / (MinDistance + Attenuation * (max(Distance, MinDistance) - MinDistance))


As you can see, adding realism to your 2D or 3D environment is easy with audio spatialization.
If you think you are ready with audio, you can now jump to the network tutorials.