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<title>Lesson 2: Looping and Fade-away</title>
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OpenAL Tutorials from DevMaster.net. Reprinted with Permission.<br>
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<p align="left" class="title"><span class="title"><font size="5">Looping and
Fade-away</font></span><font size="4"><br>
<b>Lesson 2</b></font></p>
<p align="right" class="title"> <span class="author">Author: <a href="mailto:lightonthewater@hotmail.com"><font color="#888888">Jesse
Maurais<br>
</font></a></span><span class="author">Adapted for Java By: <a href="mailto:athomas@dev.java.net"><font color="#888888">Athomas
Goldberg </font></a> </span></p>
<p><a href="http://download.java.net/media/joal/webstart/joal-lesson2.jnlp">Launch the Demo via Java Web Start</a></p>
<p align="justify">Hope you found the last tutorial of some use. I know I did. This will be a
real quick and easy tutorial. It won't get too much more complicated at this point.</p>
<pre >
<font color="#0000FF">import </font>java.nio.ByteBuffer;
<font color="#0000FF">import </font>net.java.games.joal.AL;
<font color="#0000FF">import</font> net.java.games.joal.ALC;
<font color="#0000FF">import</font> net.java.games.joal.ALFactory;
<font color="#0000FF">import</font> net.java.games.joal.util.ALut;
<font color="#0000FF">public</font> <font color="#0000FF">class</font> LoopingAndFadeaway {
<font color="#0000FF">static</font> <font color="#0000FF">int</font>[] buffer = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#0000FF">static</font> <font color="#0000FF">int</font>[] source = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] sourcePos = { 0.0f, 0.0f, 0.0f };
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] sourceVel = { 0.0f, 0.0f, 0.1f };
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerPos = { 0.0f, 0.0f, 0.0f };
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerVel = { 0.0f, 0.0f, 0.0f };
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerOri = { 0.0f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f };
<font color="#0000FF">static</font> AL al;
<font color="#0000FF">static</font> ALC alc;</p></pre>
<p align="justify">There is only one change in the code since the last tutorial
in this fist section. It is that we altered the sources velocity. It's 'z' field
is now 0.1.</p>
<pre class=code>
<font color="#0000FF">static</font> <font color="#0000FF">int</font> loadALData() {
<font color="#0000FF">if</font> (al.alGetError() != AL.AL_NO_ERROR) {
<font color="#0000FF">return</font> AL.AL_FALSE;
}
<font color="#0000FF">int</font>[] format = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#0000FF">int</font>[] size = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
ByteBuffer[] data = <font color="#0000FF">new</font> ByteBuffer[1];
<font color="#0000FF">int</font>[] freq = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#0000FF">int</font>[] loop = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#006600"> // Load wav data into a buffer.</font>
al.alGenBuffers(1, buffer);
<font color="#0000FF">if </font>(al.alGetError() != AL.AL_NO_ERROR)
<font color="#0000FF">return</font> AL.AL_FALSE;
ALut.alutLoadWAVFile(
"wavdata/Footsteps.wav",
format,
data,
size,
freq,
loop);
al.alBufferData(buffer[0], format[0], data[0], size[0], freq[0]);
ALut.alutUnloadWAV(format[0], data[0], size[0], freq[0]);
al.alGenSources(1, source);
al.alSourcei(source[0], AL.AL_BUFFER, buffer[0]);
al.alSourcef(source[0], AL.AL_PITCH, 1.0f);
al.alSourcef(source[0], AL.AL_GAIN, 1.0f);
al.alSourcefv(source[0], AL.AL_POSITION, sourcePos);
al.alSourcefv(source[0], AL.AL_POSITION, sourceVel);
al.alSourcei(source[0], AL.AL_LOOPING, AL.AL_TRUE);
<font color="#0000FF"> if </font>(al.alGetError() != AL.AL_NO_ERROR) {
<font color="#0000FF">return</font> AL.AL_FALSE;
}
<font color="#0000FF">return</font> AL.AL_TRUE;
}</pre>
<p align="justify">Two changes in this section. First we are loading the file
"Footsteps.wav". We are also explicitly setting the sources 'AL_LOOPING'
value to 'AL_TRUE'. What this means is that when the source is prompted to play
it will continue to play until stopped. It will play over again after the sound
clip has ended.</p>
<pre class=code>
<font color="#0000FF">static <span class=codeKeyword>void</span> </font>setListenerValues() {
al.alListenerfv(AL.AL_POSITION, listenerPos);
al.alListenerfv(AL.AL_VELOCITY, listenerVel);
al.alListenerfv(AL.AL_ORIENTATION, listenerOri);
}
<font color="#0000FF">static <span class=codeKeyword>void</span> </font>killALData() {
al.alDeleteBuffers(1, buffer);
al.alDeleteSources(1, source);
Alut.alutExit();
}
</pre>
<p>Nothing has changed here.</p>
<pre class=code>
<font color="#0000FF">public static void main</font>(String[] args) {
ALut.alutInit();
al = ALFactory.getAL();
<font color="#0000FF">if</font>(loadALData() == AL.AL_FALSE) {
System.exit(1);
};
setListenerValues();
al.alSourcePlay(source[0]);
<font color="#0000FF">long</font> startTime = System.currentTimeMillis();
<font color="#0000FF">long</font> elapsed = 0;
<font color="#0000FF">long</font> ticker = 0;
<font color="#0000FF">long</font> lastTime = 0;
<font color="#0000FF">while</font> (elapsed < 5000) {
elapsed = System.currentTimeMillis() - startTime;
<font color="#0000FF">if</font> (ticker > 100) {
ticker = 0;
sourcePos[0] += sourceVel[0];
sourcePos[1] += sourceVel[1];
sourcePos[2] += sourceVel[2];
al.alSourcefv(
source[0],
AL.AL_POSITION,
sourcePos);
}
ticker += System.currentTimeMillis() - lastTime;
lastTime = System.currentTimeMillis();
}
ALut.alutExit();
}
}</pre>
<p align="justify">The only thing that has changed in this code is the loop. Instead
of playing and stopping the audio sample it will slowly get quieter as the sources
position grows more distant. We do this by slowly incrementing the position
by it's velocity over time. The time is sampled by checking the system clock
which gives us a tick count. It shouldn't be necessary to change this, but if
the audio clip fades too fast you might want to change 100 to some higher number.
</p>
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