SFX ReverbのDry Levelを距離減衰・指向性音源による減衰でコントロールするためのコンポーネント

MixerParamAttenuation.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Audio;

[RequireComponent(typeof(AudioSource))]
public class MixerParamAttenuation : MonoBehaviour {
    AudioSource source;
    AudioMixerGroup mixer;
    Transform mainCamera;

    [SerializeField]
    float maxLevel = 0.0f;

    [SerializeField]
    float minLevel = -3000.0f;

    [SerializeField]
    float minAngle = 10.0f;

    [SerializeField]
    float maxAngle = 180.0f;

    [SerializeField]
    string ParameterName = "UnityChanDistance";

    [SerializeField]
    float distanceRatio;

    [SerializeField]
    float directionalRatio;

    [SerializeField]
    float angle;

    private void Start() {
        source = GetComponent<AudioSource>();
        mixer = source.outputAudioMixerGroup;
        mainCamera = Camera.main.transform;
    }

    float CalcDistanceAttenuation() {
        var distance = Vector3.Distance(transform.position, mainCamera.position);
        var minDistance = source.minDistance;
        var maxDistance = source.maxDistance;
        var ratio = (distance - minDistance) / (maxDistance - minDistance);
        if (ratio < 0.0f) {
            ratio = 0.0f;
        }
        var invRatio = 1.0f - ratio;
        var invSquareRatio = Mathf.Pow(invRatio, 2.0f);
        return invSquareRatio;
    }

    float CalcDirectionalAttenuation() {
        var sourceToCamera = mainCamera.position - source.transform.position;
        var sourceDirection = source.transform.forward;
        Debug.DrawRay(source.transform.position, sourceToCamera);
        Debug.DrawRay(source.transform.position, sourceDirection, Color.red);
        angle = Vector3.Angle(sourceDirection, sourceToCamera);
        var ratio = (angle - minAngle) / (maxAngle - minAngle);
        if (ratio < 0.0f) {
            ratio = 0.0f;
        }
        var invRatio = 1.0f - ratio;
        var invSquareRatio = Mathf.Pow(invRatio, 2.0f);
        return invSquareRatio;
    }

    private void Update() {
        // 距離減衰
        distanceRatio = CalcDistanceAttenuation();
        // 指向性音源
        directionalRatio = CalcDirectionalAttenuation();

        var ratio = distanceRatio * directionalRatio;
        var dryLevel = Mathf.Lerp(minLevel, maxLevel, ratio);

        mixer.audioMixer.SetFloat(ParameterName, dryLevel);
    }
}