Jackson's latest "Hobbit" update takes his loyal fellowship into the screenwriting process. According to the director, there are three distinct phases in a film script's life: pre-production, production, and post.

"First, it exists before the film starts shooting," he writes in his latest Facebook entry. "In this period, which can last from months to years, the script is a theoretical document — an imaginative version of the movie."

In the second phase — production — the script evolves because the movie comes into sharper focus through working on sets, bringing actors on board and the overall experience of shooting a picture. Jackson describes this as a "fun and satisfying" process, but not one without some headaches; sometimes, script revisions result in actors having to learn lines with only hours to go before shooting starts. The director illustrates these complications through a great anecdote involving "Lord of the Rings" actor (and current "Game of Thrones" star) Sean Bean.

"The worst case of this came during The Fellowship of the Ring, when we revised Boromir's long speech about Mordor at the last minute and only got it to Sean Bean on the day it was being shot," he recalls. "Sean handled it very cleverly — if you look at the movie, you'll see he occasionally has his head bowed, as if dealing with the emotional weight of the horrors of Mordor. In actual fact, the new script page had been taped to his knee! By the time we were done with several takes and a few different camera angles, Sean had the speech down pat, and it was mainly those takes that were used in the final cut."

The final phase of the scriptwriting process comes in editing, when both the pre-imagined and actually shot versions of the story no longer matter as much as the final cut.

"No matter what you were imagining when you wrote the script, and what you imagined during the shoot, nothing now matters beyond the actual cut film," he explains. "We often find that script work continues during post, including writing and shooting new scenes, reorganising the order of scenes, or recording additional dialogue to slip into shots. We do all of these things, and the writing only stops when the film is finally finished."

What do you think of Jackson's thoughts on the screenwriting process? Have you been following his "Hobbit" updates? Tell us in the comments section and on Twitter!