unity 动态更新模型透明度

RaycastHit[] hits;

        Vector3 normal = transform.position - target.position;
        hits = Physics.RaycastAll(target.position, normal, float.PositiveInfinity, mMask);
        if (hits.Length>0)
        {
            GameObject p = hits[0].collider.gameObject;
            if (p != null)
            {

                Debug.LogError("被碰撞的物体是：" + hits.Length);
                SetMaterialsColor(p.GetComponent<Renderer>(), 0.5f);
            }
        }

private void SetMaterialsColor(Renderer _renderer, float Transpa)
    {
        Material m = _renderer.sharedMaterial;
        Color color = m.color;
        color.a = Transpa;
        m.SetColor("_Color",color);
    }