So what is Audio Occlusion really about. Well, to say it in a popular way: it's about how you hear sounds "on the other side of a wall". In most games this is solved by turning down the volume a bit and also turn down the high frequencies (or treble if you like), so it sounds "muffled".
Normally this is solved by checking if there is a clear line-of-sight from the player character to the audio-source. If the line is blocked by an item (wall/crate/person/etc.), you turn down the volume and the treble in various degrees depending of how thick the blocking item is, what material it's made of etc. And when there is a clear line-of-sight with no blocking items you hear the sound loud and clear. (Reverb is usually also tweaked a bit)
I can give you a basic example here (Sorry for the simple look, but I've just watched Tron):
I've made a similar system for Running Man, and you can read more about it here if you are interested.
Doorway Audio Occlusion
Allright, maybe it's a silly name, and I haven't really given that part much thought - maybe it should something like "Displaced Sound Propagation Model" or similar... I hope I can come up with a cool name in the future... Please feel free to suggest a name if you have any ideas. :-)
Anyway - My idea is to get a bit closer to how things work in real life. If you take the example above it wouldn't work like that "out here" among us non-digital living entities. No, instead you would of course hear the sounds from the other room through the doorway... So why don't we do just that?
Ok - let's do it then:
This might not sound like a revolution to you (or maybe it does - I don't know), but if you think about how it would affect the gameplay (besides the immersive aspect), then it could actually mean quite a bit.
Imagine that you are playing Deadlock and you are in a room with multiple doorways. With the standard "line-of-sight" occlusion model you would hear your opponent(s) through the walls, and are able to pinpoint their exact location... well through the wall like you have "x-ray-ears" or something.The sounds would be muffled, but you would still be able to hear them though the wall.
But with 'my' simple model you will instead only be able to hear through which door your opponent would enter, and maybe also how far he is from the door, but not his exact position - just like in real life.
Of course there are exceptions to this model, and it's far from perfect yet, but this small prototype has provided me with enough proof-of-concept to continue down this path.
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