3DsoundSurge FAQ: All about Wavetracing


	Can't get past all the technical mumbo jumbo on reflections and occlusions? Well here is an "real game" example with wavetracing terminology slipped in at the appropriate place.

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Aureal Semiconduct's Vortex 2 Audio Q & A - Wavetracing

Questions From: 3DsoundSurge

Answers From: Skip McIlvaine (Aureal Semiconductor)
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3DSS: Skip, I am still trying to wrap my head around what wavetracing can do. For example, if I am in a room, lets say the center of the room and fire a blank, will it sound different than if I fired that same blank facing into the corner of a room?

Skip: Wavetracing will correctly render each reflection of each sound source depending on how close to a wall or object the listener is and the sound sources are, what the material and shape each room the listener and sound sources are (i.e. a gun shot in a "bright" room like a tiled bathroom bounces off the tiles, around the corner, into the "soft" wood and carpeted room that the listener is in, rendering correct reflections, acoustic materials and occlusion on the fly as appropriate.) Not only does it render each source (and all the geometry and materials that come between it and the listener) but it also will take into account dynamic objects like opening doors, elevators, moving geometry (i.e. a listener or sound source inside a car), etc.

3DSS: Theres an awfull lot of terminology that might swamp the casual gamer. Can you descibe a scene and uses some of the terminology as it applies to what really counts, the gaming experience and not the spec sheet?

Skip: Imagine a monster crawling down a hallway that is attached to the room you're in. The door is closed. You hear him under and through the door and can tell he is about 20 feet down the hallway from the door (done with proper occlusions, transmission losses, high-frequency roll-off, reflections and acoustic materials).

You scramble to remove the cover to a ventilation shaft as your only escape. From the occlusions you can tell that the monster has reached the door. You spin around and start climbing up into the ventilation shaft. You hear the door slowly swing open behind you. A reflection gets through the opening door and tells you the monster is entering the room. The door swings all the way open and now you hear the monster directly and his reflections in the room as he stands in the open doorway (his sounds are now much brighter and louder).

You climb into the shaft and hear yourself grunt and bang in the tinny, closed space, and you can sense the monster moving towards you as his direct path and reflections start bouncing more brightly and loudly in your ears, off the shaft walls. You panic and spin around firing your gun! BLAM!! The sound is almost deafening because the reflections from your gun are so loud and echo down the shaft. The monster's screams echo into the shaft as well. Off in the distance and down the hallway through the open door, you hear footsteps of troops who have come to save you. All the noticeable sound is now seemingly coming from the open doorway (reflections are seeping through the open door and drowning out the softer, occluded sounds of the direct path) and you can tell from the other cues that they still have a ways to go before reaching the doorway.

You crawl a bit deeper into the shaft and the monster's scream's direct path can't reach your ear, so all you hear are the bounces the scream sounds make as they bounce down the shaft to your ears. You hear the sounds of footsteps "brighten" and realise the troops have reached the open doorway. Just then you reach the end of the shaft and pop out into another room. You can tell that some of the troops are still in the hallway, and some have come into the room, and they are all firing at the monster and their sounds bounce off the back wall of the hallway, into the the first room, down through the shaft and out into your room. The sole location of these sounds is now the opening of the shaft. All of the sounds appear to have been "squeezed" into the small "point source" of the shaft opening, as all other sounds are completely occluded by the walls and distance.