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diff --git a/www/devmaster/lesson6.html b/www/devmaster/lesson6.html index 3a0c5ee..36e3660 100644 --- a/www/devmaster/lesson6.html +++ b/www/devmaster/lesson6.html @@ -32,16 +32,17 @@ OpenAL Tutorials from DevMaster.net. Reprinted with Permission.<br> <p align="right" class="ArticleAuthor">Author: <a href="mailto:[email protected]">Jesse Maurais</a><br> Adapted For Java By: <a href="mailto:[email protected]">Athomas Goldberg</a></p> -<p>We've been doing some pretty simple stuff up until now that didn't require - us to be very precise in the way we've handled things. The reason for this is - that we have been writing code for simplicity in order to learn easier, rather - that for robustness. Since we are going to move into some advanced stuff soon - we will take some time to learn the proper ways. Most importantly we will learn - a more advanced way of handling errors. We will also reorganize the way we have - been loading audio data. There wasn't anything wrong with our methods in particular, - but we will need a more organized and flexible approach to the process.</p> -<p>We will first consider a few functions that will help us out a lot by the time - we have finished.</p> +<p align="justify">We've been doing some pretty simple stuff up until now that + didn't require us to be very precise in the way we've handled things. The reason + for this is that we have been writing code for simplicity in order to learn + easier, rather that for robustness. Since we are going to move into some advanced + stuff soon we will take some time to learn the proper ways. Most importantly + we will learn a more advanced way of handling errors. We will also reorganize + the way we have been loading audio data. There wasn't anything wrong with our + methods in particular, but we will need a more organized and flexible approach + to the process.</p> +<p align="justify">We will first consider a few functions that will help us out + a lot by the time we have finished.</p> <pre class=code><font color="#0000FF"><span class=codeComment><font color="#006600">/** * 1) Identify the error code. * 2) Return the error as a string. @@ -99,13 +100,13 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< <font color="#0000FF">private static</font> Vector buffers = <font color="#0000FF">new</font> Vector(); <span class=codeComment><font color="#006600">// Holds all loaded buffers.</font></span><font color="#006600"> </font><font color="#0000FF">private static</font> Vector sources<font color="#006600"> = <font color="#0000FF">new</font> </font>Vector();<font color="#006600"> <span class=codeComment>// Holds all validated sources.</span></font> </pre> -<p>Take a close look at the functions and try to understand what we are going - to be doing. Basically what we are trying to create is a system in which we - no longer have to worry about the relationship between buffers and sources. - We can call for the creation of a source from a file and this system will handle - the buffer's creation on it's own so we don't duplicate a buffer (have two buffers - with the same data). This system will handle the buffers as a limited resource, - and will handle that resource efficiently.</p> +<p align="justify">Take a close look at the functions and try to understand what + we are going to be doing. Basically what we are trying to create is a system + in which we no longer have to worry about the relationship between buffers and + sources. We can call for the creation of a source from a file and this system + will handle the buffer's creation on it's own so we don't duplicate a buffer + (have two buffers with the same data). This system will handle the buffers as + a limited resource, and will handle that resource efficiently.</p> <pre class=code><font color="#0000FF">public</font> String getALErrorString(<font color="#0000FF">int</font> err) { <span class=codeKeyword><font color="#0000FF">switch</font></span>(err) { <span class=codeKeyword><font color="#0000FF">case</font></span> AL.AL_NO_ERROR: <span class=codeKeyword><font color="#0000FF">return</font></span> "AL_NO_ERROR"; @@ -119,11 +120,11 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This function will convert an OpenAL error code to a string so it can be read - on the console (or some other device). The OpenAL sdk says that the only exception - that needs be looked for in the current version is the 'AL_OUT_OF_MEMORY' error. - However, we will account for all the errors so that our code will be up to date - with later versions.</p> +<p align="justify">This function will convert an OpenAL error code to a string + so it can be read on the console (or some other device). The OpenAL sdk says + that the only exception that needs be looked for in the current version is the + 'AL_OUT_OF_MEMORY' error. However, we will account for all the errors so that + our code will be up to date with later versions.</p> <pre class=code><font color="#0000FF">public</font> String getALCErrorString(<font color="#0000FF">int</font> err) { <span class=codeKeyword><font color="#0000FF">switch</font></span>(err) { <span class=codeKeyword><font color="#0000FF">case</font></span> ALC_NO_ERROR: <span class=codeKeyword><font color="#0000FF">return</font></span> "ALC_NO_ERROR"; @@ -137,14 +138,15 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This function will perform a similar task as the previous one accept this one - will interpret Alc errors. OpenAL and Alc share common id's, but not common - enough and not dissimilar enough to use the same function for both.</p> -<p>One more note about the function 'alGetError': The OpenAL sdk defines that - it only holds a single error at a time (i.e. there is no stacking). When the - function is invoked it will return the first error that it has received, and - then clear the error bit to 'AL_NO_ERROR'. In other words an error will only - be stored in the error bit if no previous error is already stored there.</p> +<p align="justify">This function will perform a similar task as the previous one + accept this one will interpret Alc errors. OpenAL and Alc share common id's, + but not common enough and not dissimilar enough to use the same function for + both.</p> +<p align="justify">One more note about the function 'alGetError': The OpenAL sdk + defines that it only holds a single error at a time (i.e. there is no stacking). + When the function is invoked it will return the first error that it has received, + and then clear the error bit to 'AL_NO_ERROR'. In other words an error will + only be stored in the error bit if no previous error is already stored there.</p> <pre class=code><font color="#0000FF">public int</font> loadALBuffer(String path) <font color="#0000FF">throws</font> IOException { <span class=codeComment><font color="#006600">// Variables to store data which defines the buffer.</font></span> <font color="#0000FF">int</font>[] format = <font color="#0000FF">new int</font>[1]; @@ -187,11 +189,12 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< </font> <span class=codeKeyword><font color="#0000FF">return</font></span> buffer[0]; } </pre> -<p>As you can see we do an error check at every possible phase of the load. Any - number of things can happen at this point which will cause an error to be thrown. - There could be no more system memory either for the buffer creation or the data - to be loaded, the wav file itself may not even exist, or an invalid value can - be passed to any one of the OpenAL functions which will generate an error.</p> +<p align="justify">As you can see we do an error check at every possible phase + of the load. Any number of things can happen at this point which will cause + an error to be thrown. There could be no more system memory either for the buffer + creation or the data to be loaded, the wav file itself may not even exist, or + an invalid value can be passed to any one of the OpenAL functions which will + generate an error.</p> <pre class=code><font color="#0000FF">public int </font>getLoadedALBuffer(String path) <font color="0000ff">throws</font> IOException { <span class=codeKeyword><font color="#0000FF">int</font></span> count = 0; <span class=codeComment><font color="#006600">// 'count' will be an index to the buffer list.</font></span> @@ -220,16 +223,16 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This will probably be the piece of code most people have trouble with, but - it's really not that complex. We are doing a search through a list which contains - the file paths of all the wav's we have loaded so far. If one of the paths matches - the one we want to load, we will simply return the id to the buffer we loaded - it into the first time. This way as long as we consistently load our files through - this function, we will never have buffers wasted due to duplication. Every file - loaded this way must also be kept track of with it's own list. The 'buffers' - list is parallel to the 'loadedFiles' list. What I mean by this is that every - buffer in the index of 'buffers', is the same path of the index in 'loadedFiles' - from which that buffer was created.</p> +<p align="justify">This will probably be the piece of code most people have trouble + with, but it's really not that complex. We are doing a search through a list + which contains the file paths of all the wav's we have loaded so far. If one + of the paths matches the one we want to load, we will simply return the id to + the buffer we loaded it into the first time. This way as long as we consistently + load our files through this function, we will never have buffers wasted due + to duplication. Every file loaded this way must also be kept track of with it's + own list. The 'buffers' list is parallel to the 'loadedFiles' list. What I mean + by this is that every buffer in the index of 'buffers', is the same path of + the index in 'loadedFiles' from which that buffer was created.</p> <pre class=code><font color="#0000FF">public static int </font>loadALSample(String path, <span class=codeKeyword><font color="#0000FF">boolean</font></span> loop) <font color="0000ff">throws</font> IOException { <font color="#0000FF">int</font>[] source = <font color="0000ff">new int</font>[1]; <font color="0000ff">int</font> buffer; @@ -260,11 +263,11 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< <span class=codeKeyword><font color="0000ff">return</font></span> source[0]; } </pre> -<p>Now that we have created a system which will handle the buffers for us, we - just need an extension to it that will get the sources. In this code we obtain - the result of a search for the file, which is the buffer id that the file was - loaded into. This buffer is bound to the new source. We save the source id internally - and also return it.</p> +<p align="justify">Now that we have created a system which will handle the buffers + for us, we just need an extension to it that will get the sources. In this code + we obtain the result of a search for the file, which is the buffer id that the + file was loaded into. This buffer is bound to the new source. We save the source + id internally and also return it.</p> <pre class=code><span class=codeKeyword><font color="#0000FF">public static void</font></span><font color="#0000FF"> </font>killALLoadedData() { loadedFiles.clear(); } @@ -287,13 +290,13 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>We have seen the function in previous tutorials. It will represent the part - of a program which loads all wav's used by the program. In it we can see why - our system is useful. Even though we have made a call to load the same wav file - into two distinct sources, the buffer for the file 'phaser.wav' will only be - created once, and the sources 'gPhaser1' and 'gPhaser2' will both use that buffer - for playback. There is no more concern for handling buffers because the system - will handle them automatically.</p> +<p align="justify">We have seen the function in previous tutorials. It will represent + the part of a program which loads all wav's used by the program. In it we can + see why our system is useful. Even though we have made a call to load the same + wav file into two distinct sources, the buffer for the file 'phaser.wav' will + only be created once, and the sources 'gPhaser1' and 'gPhaser2' will both use + that buffer for playback. There is no more concern for handling buffers because + the system will handle them automatically.</p> <pre class=code><span class=codeKeyword><font color="#0000FF">public static void</font></span><font color="#0000FF"> </font>killALData() { <font color="006600"> <span class=codeComment>// Release all buffer data.</span> @@ -311,10 +314,10 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< sources.clear(); } </pre> -<p>All along we have been storing the buffer and source id's into stl vectors. - We free all the buffers and sources by going through them and releasing them - individually. After which we destroy the lists themselves. All we need to do - now is catch the OpenAL errors that we have thrown.</p> +<p align="justify">All along we have been storing the buffer and source id's into + stl vectors. We free all the buffers and sources by going through them and releasing + them individually. After which we destroy the lists themselves. All we need + to do now is catch the OpenAL errors that we have thrown.</p> <pre class=code> <span class=codeKeyword><font color="#0000FF">try</font></span> { initOpenAL(); loadALData(); @@ -323,14 +326,14 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>If something has gone wrong during the course of the load we will be notified - of it right away. When we catch the error it will be reported on the console. - We can use this for debugging or general error reporting. </p> -<p>That's it. A more advanced way of reporting errors, and a more robust way of - loading your wav files. We may find we need to do some modifications in the - future to allow for more flexibility, but for now we will be using this source - for basic file loading in future tutorials. Expect future tutorials to expand - on this code.</p> +<p align="justify">If something has gone wrong during the course of the load we + will be notified of it right away. When we catch the error it will be reported + on the console. We can use this for debugging or general error reporting. </p> +<p align="justify">That's it. A more advanced way of reporting errors, and a more + robust way of loading your wav files. We may find we need to do some modifications + in the future to allow for more flexibility, but for now we will be using this + source for basic file loading in future tutorials. Expect future tutorials to + expand on this code.</p> <table border="0" cellspacing="1" style="border-collapse: collapse" width="100%" id="AutoNumber2" bgcolor="#666699"> <tr> <td width="40%"> <p dir="ltr"><font color="#FFFFFF" size="2">� 2003 DevMaster.net. diff --git a/www/devmaster/lesson7.html b/www/devmaster/lesson7.html index ddb54a3..4a716da 100644 --- a/www/devmaster/lesson7.html +++ b/www/devmaster/lesson7.html @@ -33,138 +33,144 @@ OpenAL Tutorials from DevMaster.net. Reprinted with Permission.<br> Maurais</a><br> Adapted For Java By: <a href="mailto:[email protected]">Athomas Goldberg</a></p> <h1>A Look at Real-World Physics</h1> -<p>I know this will be boring review for anyone with a course in high school -physics, but lets humour ourselves. The Doppler effect can be a very tricky -concept for some people, but it is a logical process, and kind of interesting -when you get right down to it. To begin understanding the Doppler effect we -first must start to understand what a "sound" really is. Basically a sound is -your minds interpretation of a compression wave that is traveling through the -air. Whenever the air becomes disturbed it starts a wave which compresses the -air particles around it. This wave travels outward from it's point of origin. -Consider the following diagram.</p> -<p><img src="sound_waves.jpg" width="150" height="132" hspace="5" vspace="0" border="0" align="left">In this diagram -(on the left) the big red "S" stands for the sources position, and the big -red "L" stands for (you guessed it), the Listener's position. Both source and -Listener are not moving. The source is emitting compression waves outward, which -are represented in this diagram by the blue circles. The Listener is -experiencing the sound exactly as it is being made in this diagram. The Doppler -effect is not actually present in this example since there is no motion; the -Doppler effect only describes the warping of sound due to motion.</p> -<p>What you should try to do is picture this diagram animated. When the source -emits a wave (the circles) it will look as though it is growing away from it's -point of origin, which is the sources position. A good example of a similar -effect is the ripples in a pond. When you throw a pebble into a calm body of -water it will emit waves which constantly move away from the point of impact. -Believe it or not this occurs from the exact same physical properties. But what -does this have to do with the Doppler effect? Check out the next diagram (on the -right).</p> +<p align="justify">I know this will be boring review for anyone with a course + in high school physics, but lets humour ourselves. The Doppler effect can be + a very tricky concept for some people, but it is a logical process, and kind + of interesting when you get right down to it. To begin understanding the Doppler + effect we first must start to understand what a "sound" really is. + Basically a sound is your minds interpretation of a compression wave that is + traveling through the air. Whenever the air becomes disturbed it starts a wave + which compresses the air particles around it. This wave travels outward from + it's point of origin. Consider the following diagram.</p> +<p align="justify"><img src="sound_waves.jpg" width="150" height="132" hspace="5" vspace="0" border="0" align="left">In + this diagram (on the left) the big red "S" stands for the sources + position, and the big red "L" stands for (you guessed it), the Listener's + position. Both source and Listener are not moving. The source is emitting compression + waves outward, which are represented in this diagram by the blue circles. The + Listener is experiencing the sound exactly as it is being made in this diagram. + The Doppler effect is not actually present in this example since there is no + motion; the Doppler effect only describes the warping of sound due to motion.</p> +<p align="justify">What you should try to do is picture this diagram animated. + When the source emits a wave (the circles) it will look as though it is growing + away from it's point of origin, which is the sources position. A good example + of a similar effect is the ripples in a pond. When you throw a pebble into a + calm body of water it will emit waves which constantly move away from the point + of impact. Believe it or not this occurs from the exact same physical properties. + But what does this have to do with the Doppler effect? Check out the next diagram + (on the right).</p> -<p> -<img src="doppler_effect.jpg" width="150" height="132" hspace="5" border="0" align="right">Wow, what's going on here? The source is now in motion, indicated by the -little red arrow. In fact the source is now moving towards the Listener with an -implied velocity. Notice particularly that the waves (circles) are being -displaced inside each other. The displacement follows the approximate path of -the source which emits them. This is the key to the Doppler effect. Essentially -what has happened is that the source has emitted a wave at different points in -it's path of travel. The waves it emits do not move with it, but continue on -their own path of travel from the point they were emitted.</p> -<p>So how does this effect the perceived sound by the Listener? Well, notice too -in the last diagram that the waves (circles) that are between the source and the -Listener are kind of compressed together. This will cause the sound waves to run -together, which in turn causes the perceived sound seem like it's faster. What -we are talking about here is frequency. The distances between the waves effects -the frequency of the sound. When the source that emits the sound is in motion, -it causes a change in frequency. You may notice too that distance between the -waves varies at different points in space. For example, on the opposite side of -the moving source (anywhere along the previous path of travel) the distances are -actually wider, so the frequency will be lower (the distance and frequency have -an inverse relationship). What this implies is that the frequency perceived by -the Listener is relative to where the Listener is standing. </p> -<p>The motion of the Listener can also affect the frequency. This one is a -little harder to picture though. If the source is still, and the Listener is -moving toward the source, then the perceived frequency by the Listener will be -warped in the same exact manner that we described for the moving source. </p> +<p align="justify"> <img src="doppler_effect.jpg" width="150" height="132" hspace="5" border="0" align="right">Wow, + what's going on here? The source is now in motion, indicated by the little red + arrow. In fact the source is now moving towards the Listener with an implied + velocity. Notice particularly that the waves (circles) are being displaced inside + each other. The displacement follows the approximate path of the source which + emits them. This is the key to the Doppler effect. Essentially what has happened + is that the source has emitted a wave at different points in it's path of travel. + The waves it emits do not move with it, but continue on their own path of travel + from the point they were emitted.</p> +<p align="justify">So how does this effect the perceived sound by the Listener? + Well, notice too in the last diagram that the waves (circles) that are between + the source and the Listener are kind of compressed together. This will cause + the sound waves to run together, which in turn causes the perceived sound seem + like it's faster. What we are talking about here is frequency. The distances + between the waves effects the frequency of the sound. When the source that emits + the sound is in motion, it causes a change in frequency. You may notice too + that distance between the waves varies at different points in space. For example, + on the opposite side of the moving source (anywhere along the previous path + of travel) the distances are actually wider, so the frequency will be lower + (the distance and frequency have an inverse relationship). What this implies + is that the frequency perceived by the Listener is relative to where the Listener + is standing. </p> +<p align="justify">The motion of the Listener can also affect the frequency. This + one is a little harder to picture though. If the source is still, and the Listener + is moving toward the source, then the perceived frequency by the Listener will + be warped in the same exact manner that we described for the moving source. +</p> <p>If you still have trouble picturing this, consider the following two diagrams:</p> <p align="center"><img border="0" src="sin_wave.jpg" width="255" height="135"> <img border="0" src="compress_sin_wave.jpg" width="255" height="135"></p> -<p>These two diagrams will represent the sound in the form of a sine wave. Look -at the first one. Think of the peaks as the instance of the wave. The very top -point of the wave will be the same as the instance of the blue circle in the -previous set of diagrams. The valleys will be like the spaces in between the -blue circles. The second diagram represents a compressed wave. When you compare -the two you will notice an obvious difference. The second diagram simply has -more wave occurrences in the same amount of space. Other ways of saying this are -that they occur more often, with a greater regularity, or with a greater -frequency. </p> -<p>For anyone who is interested in some added information: The velocity of the -waves is the speed of sound. If the velocity of the source is greater than that -of the wave, then the source is breaking the sound barrier.</p> +<p align="justify">These two diagrams will represent the sound in the form of + a sine wave. Look at the first one. Think of the peaks as the instance of the + wave. The very top point of the wave will be the same as the instance of the + blue circle in the previous set of diagrams. The valleys will be like the spaces + in between the blue circles. The second diagram represents a compressed wave. + When you compare the two you will notice an obvious difference. The second diagram + simply has more wave occurrences in the same amount of space. Other ways of + saying this are that they occur more often, with a greater regularity, or with + a greater frequency. </p> +<p align="justify">For anyone who is interested in some added information: The + velocity of the waves is the speed of sound. If the velocity of the source is + greater than that of the wave, then the source is breaking the sound barrier.</p> <h1>The Physics of OpenAL</h1> -<p>Ok, either you have understood my ramblings on the Doppler effect from above, -or you have skipped it because you already have full knowledge of the Doppler -effect and just want to know how it effects the OpenAL rendering pipeline. I -think the best start to his section will be to quote the OpenAL spec directly:</p> +<p align="justify">Ok, either you have understood my ramblings on the Doppler + effect from above, or you have skipped it because you already have full knowledge + of the Doppler effect and just want to know how it effects the OpenAL rendering + pipeline. I think the best start to his section will be to quote the OpenAL + spec directly:</p> <blockquote> - <p><i>"The Doppler Effect depends on the velocities of Source and Listener - relative to the medium, and the propagation speed of sound in that medium." - - chapter 3, subsection 7"</i></p> + <p align="justify"><i>"The Doppler Effect depends on the velocities of + Source and Listener relative to the medium, and the propagation speed of sound + in that medium." - chapter 3, subsection 7"</i></p> </blockquote> -<p>We can take this to mean that there are 3 factors which are going to affect -the final frequency of the sound heard by the Listener. These factors are the -velocity of the source, the velocity of the Listener, and a predefined speed of -sound. </p> -<p>When we refer to a "medium", what we mean is the kind of material that both -the source and Listener are "in". For example, sounds that are heard from -underwater are much different than sounds that are heard in the open air. Air -and water are examples of different mediums. The reason that sound is so -different between these mediums has to do with the particle density. As we said -before, sound is nothing but the motion of particles in the air. In a medium -with a much greater particle density the sound will be much different because -the particles are in closer contact. When they are in closer contact it allows -for the wave to travel much better. As an example of the opposite, think of -outer space. In outer space there is an extremely low particle density. In fact -there is only a few very light particles (mostly hydrogen) scattered about. This -is why no sound can be heard from space. </p> +<p align="justify">We can take this to mean that there are 3 factors which are + going to affect the final frequency of the sound heard by the Listener. These + factors are the velocity of the source, the velocity of the Listener, and a + predefined speed of sound. </p> +<p align="justify">When we refer to a "medium", what we mean is the + kind of material that both the source and Listener are "in". For example, + sounds that are heard from underwater are much different than sounds that are + heard in the open air. Air and water are examples of different mediums. The + reason that sound is so different between these mediums has to do with the particle + density. As we said before, sound is nothing but the motion of particles in + the air. In a medium with a much greater particle density the sound will be + much different because the particles are in closer contact. When they are in + closer contact it allows for the wave to travel much better. As an example of + the opposite, think of outer space. In outer space there is an extremely low + particle density. In fact there is only a few very light particles (mostly hydrogen) + scattered about. This is why no sound can be heard from space. </p> -<p>Ok, lets get back on topic. OpenAL calculates the Doppler effect internally -for us, so we need only define a few parameters that will effect the -calculation. We would do this in case we don't want a realistic rendering. -Rather if want to exaggerate or deemphasize the effect. The calculation goes -like this.</p> +<p align="justify">Ok, lets get back on topic. OpenAL calculates the Doppler effect + internally for us, so we need only define a few parameters that will effect + the calculation. We would do this in case we don't want a realistic rendering. + Rather if want to exaggerate or deemphasize the effect. The calculation goes + like this.</p> <p><span class="codeNormal"> shift = DOPPLER_FACTOR * freq * (DOPPLER_VELOCITY - l.velocity) / (DOPPLER_VELOCITY + s.velocity)</span></p> -<p>Constants are written in all caps to differentiate. The "l" and "s" variables -are the Listener and source respectively. "freq" is the initial unaltered -frequency of the emitting wave, and "shift" is the altered frequency of the -wave. The term "shift" is the proper way to address the altered frequency and -will be used from now on. This final shifted frequency will be sampled by OpenAL -for all audio streaming that is affected. </p> +<p align="justify">Constants are written in all caps to differentiate. The "l" + and "s" variables are the Listener and source respectively. "freq" + is the initial unaltered frequency of the emitting wave, and "shift" + is the altered frequency of the wave. The term "shift" is the proper + way to address the altered frequency and will be used from now on. This final + shifted frequency will be sampled by OpenAL for all audio streaming that is + affected. </p> -<p>We already know that we can define the velocity of both source and Listener -by using the 'AL_VELOCITY' field to 'alListenerfv' and 'alSourcefv'. The 'freq' -parameter comes straight from the buffer properties when it was loaded from -file. To set the constant values the following functions are provided for us.</p> +<p align="justify">We already know that we can define the velocity of both source + and Listener by using the 'AL_VELOCITY' field to 'alListenerfv' and 'alSourcefv'. + The 'freq' parameter comes straight from the buffer properties when it was loaded + from file. To set the constant values the following functions are provided for + us.</p> <pre class=code><font color="#0000FF">public void </font>alDopplerFactor(<font color="#0000FF">float</font> factor); <font color="#0000FF">public void </font>alDopplerVelocity(<font color="#0000FF">float</font> velocity); </pre> -<p>For 'alDopplerFactor' any non-negative value will suffice. Passing a negative -value will raise an error of 'AL_INVALID_VALUE', and the whole command will be -ignored. Passing zero is a perfectly valid argument. Doing this will disable the -Doppler effect and may in fact help overall performance (but won't be as -realistic). The effect of the Doppler factor will directly change the magnitude -of the equation. A value of 1.0 will not change the effect at all. Passing -anything between 0.0 and 1.0 will minimize the Doppler effect, and anything -greater than 1.0 will maximize the effect. </p> -<p>For 'alDopplerVelocity' any non-negative non-zero value will suffice. Passing -either a negative or a zero will raise an error of 'AL_INVALID_VALUE', and the -whole command will be ignored. The Doppler velocity is essentially the speed of -sound. Setting this will be like setting how fast sound can move through the -medium. OpenAL has no sense of medium, but setting the velocity will give the -effect of a medium. OpenAL also has no sense of units (kilometer, miles, -parsecs), so keep that in mind when you set this value so it is consistent with -all other notions of units that you have defined.</p></p> +<p align="justify">For 'alDopplerFactor' any non-negative value will suffice. + Passing a negative value will raise an error of 'AL_INVALID_VALUE', and the + whole command will be ignored. Passing zero is a perfectly valid argument. Doing + this will disable the Doppler effect and may in fact help overall performance + (but won't be as realistic). The effect of the Doppler factor will directly + change the magnitude of the equation. A value of 1.0 will not change the effect + at all. Passing anything between 0.0 and 1.0 will minimize the Doppler effect, + and anything greater than 1.0 will maximize the effect. </p> +<p align="justify">For 'alDopplerVelocity' any non-negative non-zero value will + suffice. Passing either a negative or a zero will raise an error of 'AL_INVALID_VALUE', + and the whole command will be ignored. The Doppler velocity is essentially the + speed of sound. Setting this will be like setting how fast sound can move through + the medium. OpenAL has no sense of medium, but setting the velocity will give + the effect of a medium. OpenAL also has no sense of units (kilometer, miles, + parsecs), so keep that in mind when you set this value so it is consistent with + all other notions of units that you have defined.</p> +</p> <table border="0" cellspacing="1" style="border-collapse: collapse" width="100%" id="AutoNumber2" bgcolor="#666699"> <tr> <td width="40%"> <p dir="ltr"><font color="#FFFFFF" size="2">� 2003 DevMaster.net. |