I use for selection of some object in scene glSelectBuffer(512,buffer)
I think that each 4 bits keep informations about one object. First keep depth, third ID, what keep the two other , second and fourth ?

Hi !

It’s never a good way to “think” that you know something, have a look at the OpenGL documentation, it explains how the selection related functions work pretty well, I guess it would not hurt to have a peek at an existing example also, there are zillions of them out there.