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A3D FAQ - A3D 2.0 / A3D 3.0

2.1 - What is Wavetracing?

Developed over many years in conjunction with clients such as NASA, Matsushita, and Disney, this new technology is a key advancement in audio processing. Aureal Wavetracing parses the 3D geometry description of a space to trace sound waves in real-time as they are reflected and occluded by passive acoustic objects in the 3D environment.

So what does that mean is plain English? When a game programmer designs the various levels in his game, he creates different rooms or environments using walls, doors, ceilings, floors, windows, and other objects. All that information is sent to your graphics card in order to draw it on screen. Aureal wavetracing uses that same data to get the dimensions of the areas and where everything is located in them so that when we render sound, we will render it accurately with all the proper occlusions, reflections, and doppler shifting.

2.2 - What are reflections and occlusions?

When we hear sound, we hear it in many different ways. The first manner we hear it in is called direct path; this mean that the sound travels from the source of the sound to our ears with nothing in between - the sound has made a direct path to our ears.

We also hear sounds through reflections; when sound leaves its source, it doesn't just travel in a straight line. Sounds spread and will bounce into walls, depending on the room or area you are in. These sounds are called reflections because the sound reflects off parts of the room: walls, ceiling, floor, doors, etc. Reflections are a more precise way of rendering what most people refer to as reverb. These reflections will sound different depending on the various characteristics of the room.

If you were to stand in a small cave and scream at the top of your lungs, it would sound completely differently then if you did that screaming while standing in your kitchen. The shape of the walls (flat vs. curved), what the walls are made out of (rock vs. drywall), how small the room area is, etc. will all change and shape the sounds differently.

When a sound bounces off an object, the resulting sound is a first order reflection. When that sound bounces off another object, its a second order reflection. This continues on to the late order reflections, or reverb as they are more commonly called.

Another method we hear sounds is after they have been occluded. Sounds do not always come from sources directly near us; they may come from behind a wall, through a partially open doorway, or through a closed window. All these sounds will be occluded; the sounds will hit the wall, the door, the window and - depending on the material it is passing through - the sound will come through very differently. The most likely effect is that the sound will be muffled. In some cases, if a wall is very thick and not porous, the sound will not pass through at all.

Aureal Wavetracing was designed to use the game's graphics geometry (where each piece of a "room" is) to create the reflections - to bounce sounds accordingly - and generate occlusions - to muffle or block out sounds accurately. This also means that each wall or door or window or other object can have different reflective and transmittance properties. A wooden door will reflect sound differently than one made out of steel. A solid concrete wall will occlude more sound than one made out of drywall.

In the A3D 2.0 API, objects can be given distinctive properties so that they reflect and occlude just like they would in the real world.

2.3 - What is reverb?

When we hear sound, we hear it in many different ways. The first manner we hear it in is called direct path; this mean that the sound travels from the source of the sound to our ears with nothing in between - the sound has made a direct path to our ears.

We also hear sounds through reflections; when sound leaves its source, it doesn't just travel in a straight line. Sounds spread and will bounce into walls, depending on the room or area you are in. These sounds are called reflections because the sound reflects off parts of the room: walls, ceiling, floor, doors, etc.

When a sound bounces off an object, the resulting sound is a first order reflection. When that sound bounces off another object, its a second order reflection. Reverb is the term given to the sum of all the late order reflections, the sounds that originate toward the end of the sound reflecting.

Reverb is good for giving the listener a sense of how big an area is. Unlike first order reflections, reverb can often impede the listener from being able to locate an object in 3D space by its sound.

2.4 - What are downloadable HRTFs?

HRTFs are used in the algorithms that provide the positioning of sounds in 3D space. HRTFs are custom measurements of an individual's head. The better the HRTF that matches your head shape, the better the 3D positional experience will be.

Beginning with either the 2048 or 2050 drivers, Aureal will be introducing downloadable HRTFs for the Vortex 2-based sound cards. While this was originally announced as an A3D 3.0 feature, it is really a feature of the sound card drivers.

It is not known if downloadable HRTFs will be supported on either the Vortex 1 or Vortex Advantage sound cards.

2.5 - Can I get reverb in A3D 2.0 games?

Yes. A3D 2.0 games that utilize the Wavetracing engine will automatically be upgraded with reverb with the A3D 3.0 drivers. This would include Heretic II, Sin, Half-Life, Descent 3, Nascar 3, etc. No code changes to the game are necessary.

How this works is that games which initialize the Wavetracing engine with the A3D 2.0 interface will have geometric reverb calculated automatically by the new A3DAPI.DLL file. Only Vortex 2-based sound cards will be able to take advantage of this. (When the Vortex Advantage drivers are updated with the reverb engine, they will benefit as well.) These games will still render reflections and occlusions as well.

Games that use the A3D 3.0 interface will just need to specify whether or not reverb is desired.

If you do not want to hear reverb in your A3D 2.0 game, then you can simply disable the Vortex's reverb engine in the Vortex 2 Control Panel. Be sure to re-enable it afterwards.


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