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- [Narrator] Hi, and
welcome to Section Four:

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Sound Spatialization and HUD.

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In this section, we will first take a look

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at what is spatialization and how SFML

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handles spatialization.

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We would then move onto
building a SoundManager class

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and deploying emitters.

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Later, we'll learn using
the SoundManager class.

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Lastly, we'd see building
a HUD class and using it.

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Now, we move onto the first
video of this section,

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Spatialization and SFML.

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In this video, we're going to take a look

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at spatialization and how
SFML uses spatialization.

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Spatialization is the act
of making something relative

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to the space it is a part of or within.

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In our daily lives, everything
in the natural world,

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by default, is spatialized.

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If a motorbike whizzes
past from left to right,

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we'll hear the sound
grow from faint to loud

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from one side, and as it passes it by,

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it will become more
prominent in the other ear

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before fading into the distance once more.

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If we can make our
videogames a little bit more

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like the real world, our players
can become more immersed.

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It is probably obvious
that the mathematics

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of spatialization will be complex.

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How do we calculate how loud a given sound

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will be in a specific speaker
based on the direction

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the sound is coming from and the distance

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from the player, the hearer
of the sound to the object

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that is making the sound, the emitter?

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Fortunately, SFML does all
the complicated stuff for us.

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All we need to do is get familiar

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with a few technical terms.

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And then, we can start using SFML

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to spatialize our sound effects.

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Let's now take a look at emitters,

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attenuation, and listeners.

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We will need to be aware of
a few pieces of information

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in order to give SFML what
it needs to do its work.

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We will need to be
aware of where the sound

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is coming from in our game world.

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This source of the sound
is called an emitter.

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In a game, the emitter could be a zombie,

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a vehicle, or in the case
of our current project,

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a fire tile.

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We already keep track of the position

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of objects in our game, so giving SFML

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the emitter location will
be quite straightforward.

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The next factor we need to be aware of

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is attenuation.

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Attenuation is the rate at
which the wave deteriorates.

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You could simplify that statement

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and make it specific to sound by saying

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that attenuation is how quickly the sound

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reduces in volume.

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It isn't technically exact,
but it's a good enough

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description for the
purposes of this section.

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The final factor we need to consider

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is the listener.

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When SFML spatializes the sound,

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where is it spatializing it relative to?

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In most games, the logical thing to do

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is use the player character.

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In our game, we will use Thomas.

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Moving onto how SFML
handles spatialization,

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SFML has a number of functions

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that allow us to handle emitters,

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attenuation, and listeners.

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Let's take a look at them hypothetically.

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Then, we will write some code

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to add spatialized sound
to our project for real.

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We can set up a sound
effect ready to be played

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as we have done so often,

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as you can see in this highlighted code.

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We can set the position of the emitter

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using the set position function

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as shown in the code here.

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As suggested in the comments,

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how exactly you obtain the coordinates

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of the emitter will probably be dependent

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upon the type of game.

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As shown here, this would be quite simple

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in the zombie arena project.

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We will have a few challenges to overcome

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when we set the position in this project.

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We can set the attenuation level

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using the line of code.

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The actual attenuation level can be

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a little ambiguous.

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The effect that you want the player to get

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might be different from the
accurate scientific formula

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used to reduce the volume over distance

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based on attenuation.

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Getting the right attenuation level

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is usually achieved by experimenting.

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Generally speaking, the higher
the level of attenuation,

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the quicker the sound
lever reduces to silence.

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Also, you might want to set a zone

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around the emitter where the volume

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is not attenuated at all.

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You might do this if the
feature isn't appropriate

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beyond a certain range or
you have a large number

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of sound sources and don't
want to overdo the feature.

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To do so, we can use the
setMinimumDistance function

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as shown here.

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With this highlighted code,
attenuation would not begin

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to be calculated until the listener

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is 150 pixels units away from the emitter.

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Some other useful functions
from the SFML library

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include the setLoop function.

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This function will tell
SFML to keep playing

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the sound over and over
when true is passed in

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as a parameter as demonstrated
by this line of code.

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The sound will continue to play

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until we ended it with this line.

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From time to time, we will want to know

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the status of a sound, playing or stopped.

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We can achieve this with
the getStatus function

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as demonstrated in this code.

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There is just one more aspect

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of using sound spatialization with SFML

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that we need to cover.

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Where is the listener?

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We can set the position of the listener

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with this code.

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This code will make all
the sounds play relative

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to that location.

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See, this is the code I'm talking about.

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This is just what we
need for the distant roar

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of a fire tile or incoming zombie.

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But for regular sound
effects such as jumping,

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this is a problem.

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We could start handling an emitter

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for the location of the player.

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Whenever we want to play a normal sound,

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we simply call setRelative to listener

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as I've shown here,
and then play the sound

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in the exact same way we have done so far.

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Here is how we might play
a normal unspatialized

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jump sound effect.

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All we need to do is call
Listener:setPosition again

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before we play any spatialized sounds.

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We now have a wide repetoire
of SFML sound functions.

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And we're ready to make some
specialized noise for real.

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In this video, we have
learned what is spatialization

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and how SFML handles spatialization.

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Great!

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In the next video, we'll see building

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the SoundManager class and
adding it to Game Engine.