GluProject

I am trying to write a code which selects graphic entities when I move them through the centre of the screen. I am using gluproject to determine the screen coordinate of each graphic entity. However I find that the boundary coordinates of the screen seem to change when I do any rotation. Why does this happen and how can I determine the current screen boundary coordinates

[vladk]

To select something on screen the best method is to use selection buffer. For more explanation and examples, you can check out the NeHe tutorials at
http://nehe.gamedev.net