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<title>DevMaster.net - OpenAL Tutorials: Lesson 2</title>
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OpenAL Tutorials from DevMaster.net. Reprinted with Permission.<br>
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<td width="47%" height="12" valign="middle"><p><b><font color="#FFFFFF">OpenAL
Tutorials</font></b></p></td>
<td width="53%" height="12" align="right" valign="middle"><p align="right"><a href="http://devmaster.net/"><font color="#66FF99">DevMaster.net</font></a></p></td>
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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>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>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>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>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>
<p><a href="lesson2.zip">Download the Java
Source and Ant Build file.</a></p>
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