And it's really difficult and time consuming!
Well, there isn't much to explain. So I'll just make it simple.
I remade (http://img696.imageshack.us/img696/3672/bowal0.png) (http://img696.imageshack.us/i/bowal0.png/) this into this (http://img19.imageshack.us/img19/8800/bowal0h.png) (http://img19.imageshack.us/i/bowal0h.png/)
Yes, I used a up-scaler, but that's just because I wanted the LINES to be correct.
And here's a screenshot.. (http://img13.imageshack.us/img13/3306/screenshotdoom200912121.th.jpg) (http://img13.imageshack.us/i/screenshotdoom200912121.jpg/)
Yes, I'll correct the height issue..
The results are satisfying, at least for me.