Gamer's Guide to 3D sound and reverb APIs

Mikael Hagén and Mark Muschett - Last updated September 8, 2002

EAX Advanced HD

As of when this was written we just started to see some games supporting this API but I have no details on exactly how developers use it. What I will offer is an overview of what’s new from a gamer’s perspective based on the demos provided with the Audigy card.

The 5 major new features of EAX Advanced HD for games are Multi-Environment, Environment Morphing, Environment Panning, Environment Reflections and Environment Filtering.  In the demos Creative Labs also show Extreme effects and Exclusion which are not available when using the Live card. Here’s a short summary of each

Multi-Environment: The Audigy chip can now render four audio environments (that is reverb effects) simultaneously. Previous versions of EAX and the Live card can only render one environment at the time. So what’s the benefit of this? In the provided demo you are located in a big room listening to the chiming of grandfather clock in the same room while you hear the laugher from a narrow corridor outside of the room. When using just one Environmental audio effect it’s hard to tell from where the laughter is coming but with the new EAX features enabled you clearly hear it comes from the corridor. The effect is quite a different and this should offer a nice improvement to games.

Environment Panning: Distant environments can now be positioned, for example an upcoming tunnel in a racing game. In the provided demo you hear it when large bunch of bats fly out of a mine. The positioning of the echoes from the curve offers a huge improvement in the aural experience of the scene. It will be interesting to see if game developers will take advantage of it. 

Environment Morphing: Offers smooth transitions from one audio environment to the next. This should prevent abrupt changes in games where you move quickly from one environment to the next. For example racing games where you go through a tunnel. In the provided demo you are walking into the mine while whistling with some sudden changes to the reverb with the morphing effect disabled. The effect is a bit subtler and not as impressive as the multi environmental audio effects but still a feature that should offer a nice improvement.

Environment reflections: Every sound source sends out sound waves in every direction. What you hear is the combination of all the sound waves that reach your ears. Some of them got there directly (called direct path), others first hit one (first order reflections) or several object (late order reflections). Reverb (Environmental Audio) is the combination of first and late order reflections. What’s new now is that EAX Advanced HD offers developers the option to position the early reflections. This should improve your ability to position objects by just listening to the echo. Unless you are a bat the advantage is of course relatively minor from a gaming perspective but it should offer a more immersive gaming experience.

This is of course similar to the reflections technology part of the wavetracing in Aureal’s A3D 2.0 but from a developers perspective it’s implemented differently. Could also be interesting to note that Aureal did it in the reverse order compared to Creative, that is they first offered positioning of first order reflections (A3D 2.0) and later introduced a reverb engine (A3D 3.0).

In the demo provided with the Audigy cards you are located in a canyon while a crow flies circles around you. You then listen to the crow flies voice as it circles and the additions of reflections most definitely increase the feeling of being located in a canyon. It’s no doubt the reflections are well positioned too. My impressions are the positioning, especially in 4-speaker mode, is better done than what the Vortex2 cards offered. It’s hard to tell if this will be the case in actual games and not just in demos created by Creative Labs though.

As with morphing early reflections compared to reverb is in most cases a more subtle improvement offering more natural transition of a reverb effect within the same environment. That is, with reflections the reverb effects when in the middle of a room will be different than when you are close to the wall. Where I expect the introduction of early reflections to offer the most significant benefit is outdoor environments.  This is an area where the current version of EAX doesn’t seem to offer a good way to simulate the feeling of being in a canyon, as was the case in the Audigy / EAX HD demo, at least no EAX games I’ve played done it really well. That this can be simulated well with early reflections is quite clear from the provided demo.

Environment Filtering: The filtering adds new control for developers to simulate the tonal nuances of wide open spaces. No demo was provided so doubtful to what if any extent this will offer a benefit for games.

Exclusion: It allows simulations of a sound reaching you through an opening like a door or window. The sound will be occluded unless it is passing the opening itself. It’s a bit unclear to me to what extent this differs from the EAX 2.0 use of occlusion. The provided demo certainly show a clear difference between EAX enabled or disable but mostly this was due to what I think is standard occlusion followed by a reverb preset.   I asked Creative about this and in response they gave the following explanation of the term exclusion:

"exclusion" is our name to describe a case where the source sound is outside a reverberant area but passing an opening to that area. As it does so, changes to the direct path of the source occur, along with changes to the listener properties (environment). This effect can be simulated in EAX 2 by combining and manipulating occlusion and obstruction parameters, but the new exclusion calls in EAX ADVANCED HD make it much easier for developers to code the effect."

Extreme effects: The new reverb engine is said to offer more complex effects not previously available. In the demo that illustrates this you are located in a mine where you first hear a whisper followed by laughter from one miner. The effect is quite impressive but hard to tell how much this differs from what the Live can achieve in the same circumstances. What I can say is that I would have found it fairly impressive even if I’ve had heard it in a movie. We asked Creative about how Extreme effects differs from what’s possible with the Live and they gave the following answer:

"Extreme Effects" describes a new class of effects made possible with EAX ADVANCED HD.The new reverb engine running on the Audigy chip is more powerful than on the Live!, and the new parameters available allow developers to create even more effects, especially using modulation of reflections and delays.“

The only soundcard that offers support for EAX Advanced HD is the Audigy series. According to Creative Labs this is unlikely to ever change, at least not until they release the successor to Audigy. It’s possible they later change their mind and let others support it or that others manage to support it anyway similar to how they now including Creative supports A3D 1.0. A more likely route if I would guess is that they offer their own extensions to DS3D that offers similar but not identical functionality.

When it comes to backwards compatibility Creative offers the following response:

Creative provides backwards compatibility for EAX via 'EAX Unified'.  EAX Unified can convert EAX 3.0 into EAX 2.0 (or EAX 1.0) as well as converting EAX 2.0 into EAX 1.0. EAX Unified is available for both Direct Sound and Open AL (via an extension).   In all cases, the developer must specifically add code to enable this functionality, and it is therefore up to the individual developer to decide if they wish to do this.  Whilst the translation technology is written to provide the best possible translation, there are certain limitations - e.g features like Environment Morphing, Environment Panning, and Environment Reflections cannot be translated into EAX 2.0 because EAX 2.0 does not expose the necessary parameters.

Also, we are working on providing better translation from EAX 3.0 to 2.0 but the 2.0 reverb is notas robust as the newer one.

We know that several of the first EAX Advanced HD games including Soldier of Fortune 2 and Star Wars Jedi Knight II: Jedi Outcast both fails to offer any backwards compatibility. However Epic Games claim Unreal Tournament 2 will which is a good sign considering how many games that are likely to use that engine. Worth noting that both Soldier of Fortune 2 and Jedi Knight II still offer 3D sound on any DS3D capable card.

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