Non Repetitive Design - Why it matters

Non-Repetitive Design – Why it matters

One of the main aspects that game developers set out to achieve when creating games is that the experience of playing it remains immersive throughout. The idea of immersion is that you can play the game without being distracted towards something that seems unnatural in its context. This is achieved not only through the game itself but also through the audio. With the audio, we ideally want realism and spontaneity in its design, much like the ‘real world’. Having minimal repetition with the audio in a game can help to indulge the gamer into complete immersion and fulfil their expectations, without interruption.

RAM budget and streaming allowance

Something that can be considered responsible for repetition within games, is the streaming allowance and RAM available for the audio content. As a sound designer in games, keeping to the correct memory usage whenever possible and ensuring you are saving space whenever possible can help to keep the size of the audio to a minimum.  A couple of ways of achieving this are as follows:

• Using audio compression to decrease the size of a file. (UDK has an in built compression available, named ‘Vorbis’.)
• Editing out silence in a sample. Silence takes up just as much space as audible sound does, so by carefully editing it out of samples you can save on file size.
• Being meticulous with Sample Rates and down-sampling files when necessary. A concept known as the ‘Nyquist Shannon Sampling Theorem’ states that you only need to sample a sound at twice its frequency in order to accurately reproduce it. For example, if the frequency content of a sound peaks at 22 khz then you would need to sample it at 44khz in order to ensure fully audibility of the sound. These method of memory saving can give promising results.

Non-repetitive design considerations

Once the above rules are adhered to, you can begin to look at ways in which you can create an unpredictable and non-repetitive soundscape for a game. The following are a couple of ideas that can be considered:

• You can use pitch shift to determine the weight or size of an object instead of using multiple samples. In most cases, a higher pitched sample can be used for a smaller object and vice versa. In terms of footsteps you can vary the pitch dependent on the surface or size of the character.
• Re-modelling a sound using pitch shift to create something else fit for another source. For example pitching a drum hit down to create a low frequency rumble.
• Pitch up/Play down – Pitch it up in your DAW and play it at half the speed in UDK to save half the size.
• Non Standard Randomization – Sound playback system that has a bias against recently triggered sounds.

In UDK, you can randomise sounds using [AmbientSoundNonLoop] or SoundCues. You can apply slight pitch, filter and volume variations to create many outcomes. Furthermore, if you deconstruct a sound of its various qualities, you can then split these qualities into individual categories, and this then allows more control over both sounds and they can be randomised and played back simultaneously. This significantly increases the combinations of playback and therefore decreases the repetition in the sound heard. An example of this could be proposed with the fundamental sounds within an explosion ; you have the sound of the initial explosion, followed by falling debris (and some other stuff). Consider that there are multiple samples of the explosion and multiple samples for the falling debris, each branched off into different randomised nodes. Using a concatenator the sounds can then be mixed and matched creating a numerous array of combinations to significantly decrease repetition.

Middleware can be used in this nature aswell, to randomly playback sounds to create different combinations. This FMOD tutoral video demonstrates on a basic scale how you can get sounds to playback differently each time to prevent repetition, in this case an explosion debris sample.

References:

-  R. Stevens, D Raybould (2011). The Game Audio tutorial. Oxford: ELSEVIER