for (int i = 0; i < trans.transform.GetComponent<Renderer>().materials.Length; i++)
        {
            trans.transform.GetComponent<Renderer>().materials[i] = PenMgr.mInstance.m_alphaMat;
        }

這樣是賦值不了的
因為

Note that like all arrays returned by Unity, this returns a copy
 
 of materials array. If you want to change some materials in it, get the value, change an entry and set materials back.

materials在unity中是值拷貝，要新建一個數組進行賦值

            Material[] newBufMat = new Material[trans.transform.GetComponent<Renderer>().materials.Length];
            for (int i = 0; i < trans.transform.GetComponent<Renderer>().materials.Length; i++)
 

            {
                newBufMat[i] = PenMgr.mInstance.m_alphaMat;
            }


            trans.transform.GetComponent<Renderer>().materials = newBufMat;