Adds extension methods for Unity's AudioSource class for volume and rolloff calculation based on distance. The CalculateVolumeAtDistance method computes the volume of the audio source at a given distance. CalculateRolloffMultiplier calculates the rolloff factor based on the distance and the AudioSource's rolloff mode.

AudioSourceExtensions.cs

public static class AudioSourceExtensions
{
    public static float CalculateVolumeAtDistance(this AudioSource source, float distance, float volumeRolloffScale = 1)
    {
        var rolloff = CalculateRolloffMultipler(source, distance, volumeRolloffScale);
        return source.volume * Mathf.Lerp(1, rolloff, source.spatialBlend);
    }

    public static float CalculateRolloffMultipler(this AudioSource source, float distance, float volumeRolloffScale = 1)
    {
        switch (source.rolloffMode)
        {
            case AudioRolloffMode.Logarithmic:
                return distance < source.maxDistance ? source.minDistance * (1f / (1f + volumeRolloffScale * (distance - 1))) : 0;
            case AudioRolloffMode.Linear:
                return Mathf.InverseLerp(source.maxDistance, source.minDistance, distance);
            case AudioRolloffMode.Custom:
                var curve = source.GetCustomCurve(AudioSourceCurveType.CustomRolloff);
                return curve.Evaluate(Mathf.InverseLerp(source.minDistance, source.maxDistance, distance));
            default:
                return 1;
        }
    }
}