I ended up writing my own algorithm for this, and being as there doesn't seem to be anything like this out there I thought I might as well share it with the world :). The code is a bit shaky and sometimes doesn't work correctly, and can only operate on simple polygons without holes.

It is fast enough to be run in realtime on xbox.

Here it is!

Could anyone give any hints on how to further improve this? I'm learning this programming stuff in my free time so i'm not brilliant at making code robust. :P

So, I think it's great that you're sharing code (it's a great opportunity to learn from feedback, too!) but I think saying "there is nothing like that out there" is not correct.

jwatte:

I think saying "there is nothing like that out there" is not correct.

Oops! What I really meant to say is that I couldn't find any implementations of a polygon clipper algorithm out there written in C#; every sample I found so far has been written in C++ and is beyond my capabilities to convert into C#.

The algorithm definetely needs improvement though, as it sometimes it doesn't work as intended and gives incorrect output data. Could someone help me improve things?

The ZMan:

That site appears to be down at the moment...

My server died...   ..currently putting new ram in and rebooting.   Try it again....

Aeon:

I've done this in C# before using another game engine.  It was to load Half-Life .map files and build the geometry from planes and perform CSG to combine the shapes.  If you care to look, it's open source (though not ported to XNA, but I could easily do that).  AmmunitionSDK