apcmag.com: Tech wizardry (More on the Lord of the Rings visual effects team)

“Massive’s job on The Lord of the Rings is to animate
battle scenes with thousands, sometimes hundreds of thousands of
fighters. The amazing thing is that the creatures on the screen
have a “brain” — they’re not dumb models, like most animations.
Each figure is like a computer game character with instructions
about where to run and who to attack. Animators get to click the
mouse and watch the action unfold.

Labrie explains: “Essentially, there’s a brain-building tool
that allows you to define an agent or creature. Let’s say that
might be a Uruk-Hai, a type of fighting orc. We go into motion
capture stage and we’ve designed a kind of motion for the Uruk-Hai.
Let’s say that it’s kind of a middle-European half-hand,
hack-and-slash technique. We’ll capture a lot of motions — attack
high, attack low, block high, block low, walk, run, die.”

Weta records as many as 200 separate motions for each of the
individual types of creatures. The movements are all put together
in a “motion tree” and made accessible to the creature’s brain.
Once the motion-capture work is done and each Uruk-Hai is given its
instructions, the battle begins.”

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