So i'm sure you know that the Doom3 source code was recently released under GPL. after the legal problems that they faced with the comically named Carmacks Reverse and Creatives Patent upon it.
So reading this you're probably thinking to yourself "It cant be that hard, all other F/OSS source code could be compiled with the 'Make' command".
Its not quite the same with this. It uses an alternative called 'scons' (www.scons.org)
"SCons is a software construction tool—that is, a superior alternative to the classic "Make" build tool that we all know and love." And fortunatley it is not all that hard to use either.
If you opted to download the zip / tar.bz2 archive rather than using git then feel free to extract that now if you havent already
To install it in any debian based distribution of linux simply open yourself up a terminal (Ctrl+Alt+T on Ubuntu) and type this:
(If it prompts you that 'This will take up an extra XX of diskspace' just press Y and continue)
once the installation has finished you will need to install some prerequisites needed in order to actually compile the source code. If you tried to compile it as it is now you may get some errors depending on the sorts of things you have done on your computer before.
Install the following like this;
Please bear in mind that i may have missed some and may have one too many ( i installed these and that fixed the errors about missing header files, it may not be as easy for you depending on your setup ) Also i dont know whether any of these need extra software packages adding if you are on a distro other than ubuntu
After doing all of that you're ready to compile move into your doom sourcecode directory and compile it like this
So now that you have the iDTech Engine you will need content. this is where you could reverse engineer the whole thing and create the content from scratch.. or copy Dooms 'base' folder into the newly created one.