How to code drag an object using a mouse in 3D space

I am using OpenGL to drag a 3D object in 3D space. Since I am totally new in OpenGL, I do not understand what other people said about mouse dragging. In fact I need a sample code + explanation, just explanation is not enough for me(unless it is simple and detailed enough). I read other forums too, but I still do not understand.

Such as these forums, I do not understand at all...

http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number开发者_StackOverflow=53232 http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=296160

My problem is How to do as written??

---

Mouse movement is in screen coordinates (2D) while object movement is in world space (3D). Therefore you need to restrict the object movement to a line or plane before translating those coordinates.

After you set your movement plane, translating screen coordinates to world coordinates is as simple as casting a ray into the scene, intersecting it with the movement plane.

So it's a two step process. Those links you posted provide more detail. If that is not enough, please show us what you've got and where you got stuck.