projecting hotspot coordinates to a flat plane

So let's say I have several different hotspots around in my panorama. Is it possible to somehow project their 3d coordinates onto a flat image (not in krpano itself, I'm running krpano inside a flex app).

For example, if the panorama is a picture of a rectangular room, and I have one hotspot in each of the corners, how would I go about creating a 2d rectangle connecting the hotspots (again, I don't want to display that inside krpano, I just want to get the 2d coordinates...)?

Mind you, I'm not interested in real-world measurements, only the shape and it's position relative to the viewpoint.

No, it doesn't. I'm sorry, I may have not been clear enough. I wanted to project the 3d position of the hotspots to the horizon plane, not the viewport, if that makes sense, and not just when they are visible, but all the time.

Anyway, I was able to solve this in the end. I calculated the 3d coordinates of the hotspots using a constant radius, and then converted those to cartesian coordinates. It's working pretty neatly.