I'm working on a portal based engine right now, and since I don't know of any portal based map editors with an open file format, I took the time and modified the source code of the original Q3Radiant. You can find it at: http://stud3.tuwien.ac.at/~e0427091 If you're interested in contributing, just drop me a line at cyberdemon@gmx.at. Regards, -phil