Fix a GUI's position relative to a 3D object

Hello guys,

probably this is nothing new to you but for me its becoming a pain.
How can I convert a 3D position of an object in the world to a 2D position in the screen so that I can place a GUI there that is always “covering” the object?

Thanks!

Camera class contains a bunch of methods for that (World-to-Screen, Screen-to-World and similar). Just take your active camera and convert coordicates using those functions.