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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>
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<p class="ArticleTitle"><font size="5">Multiple Sources<br>
</font><font size="4"><strong>Lesson 3</strong></font></p>
<p align="right" class="ArticleAuthor">Author: <a href="mailto:lightonthewater@hotmail.com">Jesse
Maurais</a><br>
Adapted for Java by: <a href="mailto:athomas@dev.java.net">Athomas Goldberg</a></p>
<p align="justify">Hello. It's been a while since my last tutorial. But better
late than never I guess. Since I'm sure your all impatient to read the latest
tutorial, I'll just jump right into it. What we hope to accomplish with this
one is to be able to play more that one audio sample at a time. Very intense
games have all kinds of stuff going on usually involving different sound clips.
It won't be hard to implement any of this though. Doing multiple sounds is similar
to doing just one.</p>
<pre>
<font color="#0000FF">import</font> java.nio.ByteBuffer;
<font color="#0000FF">import</font> java.util.Random;
<font color="#0000FF">import</font> net.java.games.joal.AL;
<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> MultipleSources {
<font color="#0000FF">static</font> AL al;
<font color="#006600">// Maximum number of buffers we will need.</font>
<font color="#0000FF">static</font> <font color="#0000FF">final</font> <font color="#0000FF">int</font> NUM_BUFFERS = 3;
<font color="#006600">// Maximum emissions we will need.</font>
<font color="#0000FF">static</font> <font color="#0000FF">final</font> <font color="#0000FF">int</font> NUM_SOURCES = 3;
<font color="#006600">// These index the buffers and sources</font>
<font color="#0000FF">static</font> <font color="#0000FF">final</font> <font color="#0000FF">int</font> BATTLE = 0;
<font color="#0000FF">static</font> <font color="#0000FF">final</font> <font color="#0000FF">int</font> GUN1 = 1;
<font color="#0000FF">static</font> <font color="#0000FF">final</font> <font color="#0000FF">int</font> GUN2 = 2;
<font color="#006600">// Buffers hold sound data</font>
<font color="#0000FF">static</font> <font color="#0000FF">int</font>[] buffers = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[NUM_BUFFERS];
<font color="#006600">// Sources are points of emitting sound</font>
<font color="#0000FF">static</font> <font color="#0000FF">int</font>[] sources = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[NUM_SOURCES];
<font color="#006600">// Position of the source sounds.</font>
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[][] sourcePos = <font color="#0000FF">new</font> <font color="#0000FF">float</font>[NUM_SOURCES][3];
<font color="#006600">// Velocity of the source sounds</font>
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[][] sourceVel = <font color="#0000FF">new</font> <font color="#0000FF">float</font>[NUM_SOURCES][3];
<font color="#006600">// Position of the listener</font>.
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerPos = { 0.0f, 0.0f, 0.0f };
<font color="#006600">// Velocity of the listener.</font>
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerVel = { 0.0f, 0.0f, 0.0f };
<font color="#006600">// Orientation of the listener. (first 3 elements are "at", second 3 are "up")</font>
<font color="#0000FF">static</font> <font color="#0000FF">float</font>[] listenerOri = { 0.0f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f };
</pre>
<p align="justify">I guess this little piece of source code will be familiar to
a lot of you who've read the first two tutorials. The only difference is that
we now have 3 different sound effects that we are going to load into the OpenAL
sound system.</p>
<pre>
<font color="#0000FF">static</font> <font color="#0000FF">int</font> loadALData() {
<font color="#006600">//variables to load into</font>
<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 buffers</font>
al.alGenBuffers(NUM_BUFFERS, buffers);
<font color="#0000FF">if </font>(al.alGetError() != AL.AL_NO_ERROR) {
<font color="#0000FF">return</font> AL.AL_FALSE;
}
ALut.alutLoadWAVFile(
"wavdata/Battle.wav",
format,
data,
size,
freq,
loop);
al.alBufferData(
buffers[BATTLE],
format[0],
data[0],
size[0],
freq[0]);
ALut.alutUnloadWAV(format[0], data[0], size[0], freq[0]);
ALut.alutLoadWAVFile(
"wavdata/Gun1.wav",
format,
data,
size,
freq,
loop);
al.alBufferData(
buffers[GUN1],
format[0],
data[0],
size[0],
freq[0]);
ALut.alutUnloadWAV(format[0], data[0], size[0], freq[0]);
ALut.alutLoadWAVFile(
"wavdata/Gun2.wav",
format,
data,
size,
freq,
loop);
al.alBufferData(
buffers[GUN2],
format[0],
data[0],
size[0],
freq[0]);
ALut.alutUnloadWAV(format[0], data[0], size[0], freq[0]);
<font color="#006600"> // bind buffers into audio sources</font>
al.alGenSources(NUM_SOURCES, sources);
al.alSourcei(sources[BATTLE], AL.AL_BUFFER, buffers[BATTLE]);
al.alSourcef(sources[BATTLE], AL.AL_PITCH, 1.0f);
al.alSourcef(sources[BATTLE], AL.AL_GAIN, 1.0f);
al.alSourcefv(sources[BATTLE], AL.AL_POSITION, sourcePos[BATTLE]);
al.alSourcefv(sources[BATTLE], AL.AL_POSITION, sourceVel[BATTLE]);
al.alSourcei(sources[BATTLE], AL.AL_LOOPING, AL.AL_TRUE);
al.alSourcei(sources[GUN1], AL.AL_BUFFER, buffers[GUN1]);
al.alSourcef(sources[GUN1], AL.AL_PITCH, 1.0f);
al.alSourcef(sources[GUN1], AL.AL_GAIN, 1.0f);
al.alSourcefv(sources[GUN1], AL.AL_POSITION, sourcePos[GUN1]);
al.alSourcefv(sources[GUN1], AL.AL_POSITION, sourceVel[GUN1]);
al.alSourcei(sources[GUN1], AL.AL_LOOPING, AL.AL_FALSE);
al.alSourcei(sources[GUN2], AL.AL_BUFFER, buffers[GUN2]);
al.alSourcef(sources[GUN2], AL.AL_PITCH, 1.0f);
al.alSourcef(sources[GUN2], AL.AL_GAIN, 1.0f);
al.alSourcefv(sources[GUN2], AL.AL_POSITION, sourcePos[GUN2]);
al.alSourcefv(sources[GUN2], AL.AL_POSITION, sourceVel[GUN2]);
al.alSourcei(sources[GUN2], AL.AL_LOOPING, AL.AL_FALSE);
<font color="#006600"> // do another error check and return</font>
if (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">This code looks quite a bit different at first, but it isn't
really. Basically we load the file data into our 3 buffers, then lock the 3
buffers to our 3 sources relatively. The only other difference is that the "Battle.wav"
(Source index 0) is looping while the rest are not.</p>
<pre>
<font color="#0000FF">static</font> <font color="#0000FF">void</font> setListenerValues() {
al.alListenerfv(AL.AL_POSITION, listenerPos);
al.alListenerfv(AL.AL_VELOCITY, listenerVel);
al.alListenerfv(AL.AL_ORIENTATION, listenerOri);
}
<font color="#0000FF">static</font> <font color="#0000FF">void</font> killAllData() {
al.alDeleteBuffers(NUM_BUFFERS, buffers);
al.alDeleteSources(NUM_SOURCES, sources);
ALut.alutExit();
}
</pre>
<p>I don't think we changed anything in this code.</p>
<pre> <font color="#0000FF">public</font> <font color="#0000FF">static</font> <font color="#0000FF">void</font> main(String[] args) {
al = ALFactory.getAL();
<font color="#006600">// Initialize OpenAL and clear the error bit</font>
ALut.alutInit();
al.alGetError();
<font color="#006600">// Load the wav data.</font>
<font color="#0000FF">if</font>(loadALData() == AL.AL_FALSE) {
System.exit(1);
}
setListenerValues();
<font color="#006600"> // begin the battle sample to play</font>
al.alSourcePlay(sources[BATTLE]);
<font color="#0000FF">long</font> startTime = System.currentTimeMillis();
<font color="#0000FF">long</font> elapsed = 0;
<font color="#0000FF">long</font> totalElapsed = 0;
Random rand = new Random();
<font color="#0000FF">int</font>[] state = <font color="#0000FF">new</font> <font color="#0000FF">int</font>[1];
<font color="#0000FF">while</font> (totalElapsed < 10000) {
elapsed = System.currentTimeMillis() - startTime;
<font color="#0000FF">if</font> (elapsed > 50) {
totalElapsed += elapsed;
startTime = System.currentTimeMillis();
<font color="#006600">// pick one of the sources at random and check to see if it is playing.
// Skip the first source because it is looping anyway (will always be playing).</font>
<font color="#0000FF">int</font> pick = Math.abs((rand.nextInt()) % 2) + 1;
al.alGetSourcei(sources[pick], AL.AL_SOURCE_STATE, state);
<font color="#0000FF">if</font> (state[0] != AL.AL_PLAYING) {
<font color="#006600"> // pick a random position around the listener to play the source.</font>
<font color="#0000FF">double</font> theta = (rand.nextInt() % 360) * 3.14 / 180.0;
sourcePos[pick][0] = - ((<font color="#0000FF">float</font>) Math.cos(theta));
sourcePos[pick][1] = - ((<font color="#0000FF">float</font>) (rand.nextInt() % 2));
sourcePos[pick][2] = - ((<font color="#0000FF">float</font>) Math.sin(theta));
al.alSourcefv(
sources[pick],
AL.AL_POSITION,
sourcePos[pick]);
al.alSourcePlay(sources[pick]);
}
}
}
killAllData();
}
}
</pre>
<p align="justify">Here is the interesting part of this tutorial. We go through
each of the sources to make sure it's playing. If it is not then we set it to
play but we select a new point in 3D space for it to play (just for kicks).
</p>
<p align="justify">And bang! We are done. As most of you have probably seen, you
don't have to do anything special to play more than one source at a time. OpenAL
will handle all the mixing features to get the sounds right for their respective
distances and velocities. And when it comes right down to it, isn't that the
beauty of OpenAL? </p>
<p align="justify">You know that was a lot easier than I thought. I don't know
why I waited so long to write it. Anyway, if anyone reading wants to see something
specific in future tutorials (not necessarily pertaining to OpenAL, I have quite
an extensive knowledge base) drop me a line at <a href="mailto:lightonthewater@hotmail.com">lightonthewater@hotmail.com</a>
I plan to do tutorials on sharing buffers and the Doppler effect in some later
tutorial unless there is request for something else. Have fun with the code!</p>
<p><a href="lesson3.zip">Download the Java
source and Ant build file</a></p>
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