FadeAudio

Description

This mechanic shows how to fade in and out background audio at the beginning or end of the audio.

Implementation

The code itself is straightforward:

using UnityEngine;

namespace Audio
{
    public class FadeAudio : MonoBehaviour
    {
        public bool fadeOnAudioEnd = true;
        public bool fadeOnAudioStart = true;
        public float fadeTime;

        public float minVolume = 0;
        public float maxVolume = 1;

        public AudioSource source;

        public void Play()
        {
            source.volume = minVolume;
            source.Play();
        }

        private void Update()
        {
            if (source == null || source.clip == null || source.clip.length == 0)
            {
                return;
            }

            // Fade at the beginning
            if (fadeOnAudioStart && source.time < fadeTime)
            {
                // Smoothly increase volume
                source.volume = Mathf.Lerp(minVolume, maxVolume, source.time / fadeTime);
            }
            // Fade at the end
            else if (fadeOnAudioEnd && source.clip.length - source.time < fadeTime)
            {
                // Smoothly decrease volume
                source.volume = Mathf.Lerp(minVolume, maxVolume, (source.clip.length - source.time) / fadeTime);
            }
            else
            {
                // If no fade is needed, keep volume at max
                source.volume = maxVolume;
            }
        }
    }
}

To set it up:

Ensure there is an AudioListener component on your main camera.
Add an AudioSource component and assign an audio clip.
Optionally, click the Loop option to on if you want the audio to loop.
Add a FadeAudio component and assign the source property to the audio source you just created.
Change the Fade Time property to however long you want the audio to fade in/out for.

Example Project

It can be viewed here

There are no enemies or controls. The text displays the amount into the audio clip the source currently is, and the volume of the source. The slider lets the user seek to any part of the audio, so that the fade in and out can more easily be heard.

Challenges

This wasn't particularly challenging, especially because I've implemented similar systems in other games. It took about an hour, although I spent another hour figuring out what to do for this assignment.

Credits