How to use glutBitmapCharactor in 3D space


I want to display some text in OpenGL window(X window system). How can I use glutBitmapCharacter in 3D space?I don’t know its timing.

Should I use gluOrtho2D?I don’t know how to use this function and retain 3D matrix and 2D matrix steady.

I want to receive any advice.

sorry, my broken English.

thank you very much.