Swayer.cs

//Steffen Vetne made this
//Creative Commons 0

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

[ExecuteInEditMode]
public class Swayer : MonoBehaviour
{
    //Fields
    public Vector3 rotationOffset = Vector3.zero;
    public Vector3 axis = Vector3.right;

    [Header("Animation")]
    public AnimationCurve swayAnimation = null;
    public float swayOffset = 0;
    public float swayMultiplier = 20;
    public float swayFinalOffset = 0;

    [Header("Time")]
    public Vector2 randomStartTime = new Vector2(0, 10);
    public float rateMultiplier = 1;
    public Vector2 randomRate = new Vector2(1, 2);

    private float t;
    private float rate;



    //Lifecycle
#if UNITY_EDITOR
    private void OnValidate()
    {
        #region Default Sway Curve
        if (swayAnimation == null)
        {
            var keys = new Keyframe[3];

            var keyframe = new Keyframe(0, -1) { inTangent = 0, outTangent = 0 };
            keys[0] = keyframe;

            keyframe.time = 1;
            keyframe.value = 1;
            keys[1] = keyframe;

            keyframe.time = 2;
            keyframe.value = -1;
            keys[2] = keyframe;

            swayAnimation = new AnimationCurve() { keys = keys };
        }
        #endregion

        swayAnimation.postWrapMode = swayAnimation.preWrapMode = WrapMode.Loop;

        //OnEnable();
    }

    private void OnDrawGizmosSelected()
    {
        float size = UnityEditor.HandleUtility.GetHandleSize(transform.position) * 0.75f;

        Vector3 axis = this.axis;
        if (transform.parent != null)
            axis = transform.parent.TransformDirection(axis);

        Gizmos.DrawRay(transform.position, axis * size);
    }
#endif

    private void OnEnable()
    {
        rate = Random.Range(randomRate.x, randomRate.y);
        t = Random.Range(randomStartTime.x, randomStartTime.y);
    }

    private void Update()
    {
        t += rateMultiplier * rate * Time.deltaTime;

        float a = (swayAnimation.Evaluate(t) + swayOffset) * swayMultiplier + swayFinalOffset;

        transform.localRotation = Quaternion.AngleAxis(a, axis) * Quaternion.Euler(rotationOffset);
    }
}