How did Douglas Trumbull make the Stargate sequence in 2001 A Space Odyssey?

Extract from our story, Movie Magic:
www.abc.net.au/...
They take a long time to make and can cost millions of dollars. But there's one kid who's learning the same kind of techniques without the huge budget. And he's getting such a reputation that he's just been invited to spend some time with a famous Hollywood filmmaker.