//创建一个名为Cube的物体
GameObject go = new GameObject("Cube");
//给go添加一个刚体组件
go.AddComponent<Rigidbody>();

mMesh = go.GetComponent<MeshRenderer> ();

  public MeshRenderer mMesh;
  void Start ()
    {
     mMesh = go.GetComponent<MeshRenderer> ();
     //关闭
     mMesh.enabled = false;
     //激活
     mMesh.enabled = true;
    }

GameObject go = new GameObject("Cube");
//关闭物体
go.SetActive(false);
//激活物体
go.SetActive(true);