I'm using Matlab to create a small chess game for one of my courses this semester. The thing I'm having trouble with is having the user be able to select one of the chess pieces.

To simplify things, I'm making it so that the user selects a piece by clicking on the square that the chess piece resides on rather than clicking the piece itself (which I assume would be much more difficult). I know how to get the x and y coordinates of the view-port, but how do I transform these coordinates into 3-space coordinates?

I know that there are multiple x,y,z coordinates associated with each view-port coordinate, but I'm only interested in the x,y,z coordinate where z = 0 (since the board itself is in the x,y plane that intersects the z axis where z = 0).

Thanks!