HI, ArenMook.
Thanks for your answers.
We'v tested another way to show the 3D model and respond mouse event. We made a transparent UI with a transparent hole in it and we could show the 3d model behind the hole. In order to operate the 3d model such as using mouse rotating it, we captured the main camera mouse click event and mouse screen position in the region of the hole. It seems work.
Thank you anyway.