In addition to the main characters, "The
Prince of Egypt" features thousands of "extras,"
who would have been virtually impossible to
animate using traditional hand-drawn animation.
Through some remarkable digital innovations, the
computer animators were able to populate the film
with hundreds of thousands of people.
CG crowd animator Wendy Elwell remarks,
"Obviously, you can't tell the story of the
Exodus with only 100 characters, so `The Prince
of Egypt' required that we figure out how to put
tens of thousands of people on the screen."
The process began in the traditional way,
with the hand-drawn design of a character, which
was then modeled in the computer in 3-D. By
reshaping that initial character, the animators
were able to produce four "key" characters
representing extremes of height, weight and age.
They then took varying percentages of the four
models and blended them in different proportions
to make a database of about 20 characters.
Modifying features like skin, hair color and
clothing gave them even more variety. The
process was duplicated to create a database of
women and children as well. "It's limitless,"
Elwell states. "You can have as many characters
as you need."
The next step was to give the characters a
"skeleton," so the animators could assign
repeatable motion cycles like walking, hammering,
polishing, etc. Elwell expounds, "We could pick
from an entire library of different actions and
apply them individually as suited the character.
An old man, for example, was animated very
differently from a young woman."
Applications of what is called behavioral
software made the computer generated characters
seem actually aware of their surroundings and the
obstacles therein. To illustrate: the characters
are given parameters of space, distance and
variable speeds and set on a "path." When a
younger, faster person approaches an older,
slower one, the faster character can judge how
much space there is to go around the slower one
without bumping into him, so they don't crash
into each other.
Even though the computer generated people
could sense time and space, they didn't seem to
have much fashion sense.so to speak. Many of
them are wearing long robes, but the computer
didn't know that the fabric should not go through
the skin and vice versa. To prevent that from
happening, the clothing had to be animated along
with the character.
There was, however, one major drawback to animating the multitudes needed for
scenes like the exodus itself. The amount of data necessary to create tens of
thousands of 3-D character models would have slowed down the computer enough to
have made it nearly as impractical as hand- drawn animation. To overcome this
problem, software developer Mike Ullner designed a crowd simulation program for
scenes where the characters would only be seen from a limited perspective. The
computer could map a two- dimensional image of the animated character onto a "card"
in three-dimensional space. Instead of the thousands of data points necessary
for a 3-D model, the computer only needs the four data points of the "card" to
show the character in motion from just the audience's point-of-view. Using these
methods, "The Prince of Egypt" team was able to create a combined total of hundreds
of thousands of characters for sequences like the exodus and the Red Sea passage.
The final epilogue shot alone depicts over 146,000 fully animated characters.
