Puybaret, thank you so much. that is what I want exactly!!

BTW, I find a bug when I try to import an object file, eg zip format of a model.
I found once I imported the object file, its I/O would be locked exclusively no mater when I closed the object importing whindow until I totally exited the ...

is there any feature provided to change the position of the light source, I find it always at the position of south...