Hey,

Im just thinking about how you logically go about making a simple GUI in a simple 3d based app, such as a simple OpenGL app.

The part im wondering is how do you work out when you have clicked on an element of the GUI? as the mouse click will have an X/Y position from windows or your input system I assume, then from there do you have to convert it into worldspace to work out where in the scene you have clicked, also how do you take from your world to local space? (while we are on the subject)

I made a really simple menu system for an old 2D game a while back, but as it was 2d i didnt need to do any translations or anything on the coord. I think i just made a simple tree hierarchy to specify what menu elements sat where and it just checked down the tree to work out what was clicked...

Im just curious as i may need to write a simple 3d menu system in the future and any info to give me a headstart would be great!