3 point perspective exersize

[The_Glaive]

I'm trying to understand the basic concepts of the three point perspective assignment that was used in the thread from here
http://conceptart.org/forums/showthread.php?t=108793
and I don't think I'm even able to grasp this basic foundation of illustration.
http://img408.imageshack.us/img408/7253/3pointperspectiveexerci.th.png (http://img408.imageshack.us/i/3pointperspectiveexerci.png/)

As you can see, I'm supposed to be drawing a cube and something is way off.

Can someone try to explain this a little better for me?

[DAMJAN]

The reason no one is commenting here is because you most likely posted in the wrong section. Try here: http://www.conceptart.org/forums/forumdisplay.php?f=59