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Large Audio Sources

One of the challenges I found while working with 3D, positional audio, is how to handle large sources.

Positional audio sources are points - the sound comes from a specific location. While this works for things like animals, where the source of the sound is the animal's mouth, it does not work so for things like rivers, where there is no one point you can call the source of its sound.

There are 3 large audio sources in Midnight Island: The lake, the river, and the ocean.

I originally designed the lake as bean-shaped, but simplified it to a circle to make the audio implementation easier. The audio from the lake comes from the center of the lake, but attenuation begins at the edge of the lake - it's still at its loudest at the edge.

For the river, I simply added audio sources along it, and adjusted attenuation so the river sound does not get quiet between sources. Although the sound of the river comes from multiple points, the result is barely noticeable, and any variations in volume along the river seem natural since rivers are not uniform in sound.

The biggest challenge was the ocean; the lake lake solution wouldn't work since the sound comes from a ring around the island, and the river solution would be tedious and inefficient, which could possibly impact performance.

Instead, I created 1 audio source that moves along the coast as the player moves. Since the island is a circle centered on the origin, I was easily able to use the player's position and the radius of the Island to determine position on the coast closest to the player where the source should be.

Although the sound of the ocean properly moved around the coast, it was still a point, so where you were close to coast, you could hear the sound of the coming from a specific location instead of all around you. To solve this, I modified the spread graph in Wwise.

Spread effects how positional a sound is - a sound to the right of you with a spread of 0 plays evenly from both ears, while a sound to the right of you with a spread of 100 plays from the right ear. I adjusted the spread graph so the farther you are from the coast, the more position the audio is - that way where you're at the coast, the sound of the ocean is all around you, and when you travel further inland, you can hear what direction in the ocean is.

I also applied spread modifications to the lake and river, which improved the quality and realism of the sounds.

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