逐渐减少滑痕α

在我的汽车战争游戏中,我在汽车转弯时产生了打滑痕迹。 它工作正常,几秒钟后,我想减少它的alpha值并将其从游戏中移除。我用轨迹渲染器生成了滑痕。

• 我需要为材质指定什么材质球?
• 我怎样才能降低它的α?

目前,我已经使用了这种轨迹渲染器材质:

现在为了逐渐减少alpha,我有这样的代码:

private IEnumerator Start()
{
    Material myMaterial = GetComponent<Renderer>().material;

    while (true)
    {
        yield return new WaitForSeconds(1f);

        // check whether this skid trail has finished
        // (the Wheel script sets the parent to null when the skid finishes)
        if (transform.parent.name == "SkidTrailsDetachedParent")
        {

            // set the start colour
            //Color startCol = GetComponent<Renderer>().material.color;
            //Color startCol = myMaterial.GetColor("_EmisColor");
            Color startCol = myMaterial.GetColor("_TintColor");

            // wait for the persist time
            yield return new WaitForSeconds(persistTime);

            float t = Time.time;

            // fade out the skid mark
            while (Time.time < t + fadeDuration)
            {
                float i = Mathf.InverseLerp(t, t + fadeDuration, Time.time);
                //myMaterial.color = startCol * new Color(1, 1, 1, 1 - i);
                //myMaterial.SetColor("_EmisColor", startCol * new Color(1f, 1f, 1f, 1f - i));
                myMaterial.SetColor("_TintColor", startCol * new Color(1f, 1f, 1f, 1f - i));
                yield return null;
            }

            // the object has faded and is now done so destroy it
            Destroy(gameObject);
        }
    }
}

不过,这对我不起作用。