Coroutine control interpolation operation

float value; 

IEnumerator SmoothLerp(float start, float end, float duration)  
{
  float time = 0;
  while (time < duration) {
    float t = time / duration;  
    value = Mathf.Lerp(start, end, t); // Use value to store result
    time += Time.deltaTime;
    yield return null; 
  }
  value = end; // Set to final value
}

/// <summary>
    /// 平滑过渡实现更新云覆盖面积参数
    /// </summary>
    /// <param name="start">起始值</param>
    /// <param name="end">目标值</param>
    /// <param name="duration">时间</param>
    /// <returns></returns>
    IEnumerator SmoothUpdateCloudShapeFactor(float start, float end, float duration)
    {
        float time = 0;
        while (time < duration)
        {
            float t = time / duration;
            time += Time.deltaTime;

            shapefactor = Mathf.Lerp(start, end, t);
            GetVolumetricClouds().shapeFactor.value = shapefactor;

            yield return null;
        }
        shapefactor = end;
    }