is 3dgs`s ui is mesh of render likes unity3d`s NGUI?any one know?
If you want to know if Gamestudios UI can be rendered in 3D world: No, not really. You can render a panel to a BMAP and then render the BMAP to a sprite (ent_setskin), but you can't get input working then
You could make it with sprites or thin models and place them very close the camera and with a shader that shows them ontop of other stuff (or use ZNEAR flag but that one has some visual bugs iirc). Input could be done though draw_text but would appear weird because you cannot rotate it (I guess). If your feeling hardcore you could use draw_line3d to manually create letters. Maybe try draw_obj to show text? Or maybe convert/render the input text to bmap and show that on a sprite or such?