Design - this month in sound and vision!!
It's been another month of sound effect creation for me and, just as I predicted last month, the list of effects that I need to create gets longer and longer the more I do. That could be slightly depressing, where it not for the fact that the game is starting to sound really good. After playing the game in silence for months and months, it's beginning to come alive; not least since the introduction of Zoned sounds, which is what I'm going to talk about this month.
In last month's gripping instalment of the dev diary, I explained about combat sound effects, and about how you could have sounds coming from two locations from a single gunshot: the gun itself and the target. Those are both point sources - the sound comes from a single point and radiates out in a sphere, decaying in volume as it goes (it's slightly more complicated than that, but you get the idea). Other point sources are things like footsteps, vehicle engines, gates opening etc. The problem with point sources comes when you're trying to apply a sound to a larger object, especially one that's longer in some directions than others, like a long building, for example. Here's a picture that not only demonstrates this, but also shows why I'm not the artist on this game:
The blue bit is the sound radiating from a point source, while the brown rectangle is the building. Imagine the building's a factory, full of clanking and whirring machinery. If you were to stand a few feet from the wall, you'd hear the sound coming through the wall at a certain volume. If you then moved around and stood the same distance away from the next wall, you'd expect to hear the sound coming through at roughly the same volume, wouldn't you? Now look at the blue circle again - if you stood in the middle of the long sides, the sound is a much darker blue, and so louder, than at the short sides, because the short sides are further away from the point source in the centre of the building.
Now, one solution to this would be to have a couple of point sources, playing the same sound, placed towards opposite ends of the building; but that's not very elegant and could get very complex with long, or oddly shaped, buildings.
This is where zoned sounds come in. In the editor, zoned sounds are displayed as two boxes; a light-coloured inner and a darker coloured outer, like this:
Rather than coming from a single point, the sound is at full volume at all places inside the inner box, disappears completely at the edges of the outer box, and falls away as you move between the two. When I place down the zone in the editor, I can scale the inner box in all three dimensions, in this case making it just slightly larger than the building it represents, and I can change the distance that the sound takes to fall off - the size of the outer box essentially. Now, the more observant among you might be thinking "hang on Mike, wouldn't the outer box have rounded off corners if you were being realistic?" and technically you'd be right; if the falloff was a set distance from the centre of one of the inner box's faces, it would also be the same distance from the inner box's corners, leading to rounded edges. But, that would be very complex to model and in the game you really don't notice anyway; unless someone points it out like I've just done....curses.
I'm keeping the zoned sounds subtle, but their addition brings a great deal to the levels, especially if you have the music switched off (although you should have the music on really as it's ace); after all, there aren't many times in your life when you're in an area that's dead silent so it feels very unnatural.
So, as a final illustration, here's a recording I've made of myself moving about within a level, listening to some of the zoned sounds. I've made sure that the camera's right up next to the sound sources, so that they come across clearly, which is not really what you'd be doing in-game, but you get the idea.
