I'm trying to make it so I can drag objects, like a box, around with my mouse in a DirectX 10/Windows application. So far I only have a plane for the floor, a few boxes, and my mouse coordinates displayed to the screen. What would be the best technique to detect when my mouse is over an object? Do I need to figure out where the box edges are in terms of screen coordinates and then do a compare with my mouse coordinates? If so, how do I determine the location of an object in terms of screen coordinates instead of my world coordinate system?