This tutorial is building a Unity3D project where you are able to draw in 3D space, not just 2d drawing but 3d as well, I think it worked pretty well. if you have any suggestions please let me know.
AR control device: https://www.youtube.com/watch?v=2yft9xDgzUw
Download files from here: https://drive.google.com/file/d/0Bye6_YBzy8q3S01kcm84clpCYnM/view?usp=sharing
Don’t forget to subscribe my channel!