Narrator: For this scene in "Coco,"
Pixar's computer kept getting Mamá Imelda's skirt
caught between her skeleton joints.
So Pixar developed a whole new simulation system
and digitally wrapped every joint
with a layer of invisible fabric.
Every single Pixar movie has pushed the boundaries
of 3D animation with detailed work like this,
from lighting food with two light sources
to simulating realistic fur.
Let's pick up where we left off in part one,
with Merida's realistic-looking locks in "Brave."
Merida had a lot of hair.
If you unwound a strand of it,
it would measure 4 feet in length.
But the simulation tech hadn't yet tackled
the unique physics of curly hair,
where each curl has a springlike structure
but the overall movement of the hair is light and soft
in a way that seems to defy gravity.
Pixar's first step was to build Merida's hair in layers,
each with a different tightness of curl
to get that natural-looking variation.
The team then spent three years
developing a special simulator called Taz
that'd be powerful enough to handle
the 1,500 hand-placed curls on Merida's head.
Taz accounted for all the interactions
between different strands
while making sure that every curl held its shape.
The system also changed
the effect of gravity on Merida's hair,
using a gravity coefficient closer to the one on the moon
than the one on Earth.
With a lower gravity, the hair could keep its mass
but flow and bounce in a natural way.
To give the hair its softness,
the lighting team used a mix
of subsurface scattering and colored shadows
to imitate the complex way
curly hair scatters and transmits light.
It took two months just to nail the hair in this scene,
when Merida pulls back her hood
to reveal the full volume of curls.
But that work set the stage for Pixar
to represent all hair textures on screen in the future.
In "Cars," Pixar used ray tracing in small doses
to create reflections and shadows
in dynamic scenes with lots of shiny vehicles.
But for the vast majority of shots,
Pixar's artists still built reflections
and mapped out shadows by hand.
That changed with "Monsters University."
The lighting team wanted more time
to focus on the artistic,
rather than the engineering, side of lighting,
like creating new "scare lights" for scary monster scenes.
To streamline the process,
the goal was to ray-trace pretty much everything:
all the shadows and light refractions,
even the reflections in a character's eye.
This required an overhaul of the lighting system
the studio had used since the first "Toy Story."
Pixar built a new system called Global Illumination
that modeled the natural distribution of light in a scene,
all based on real-world physics.
Now, every time an artist placed a light source in a shot,
the computer would know how that light would travel
and interact with other elements,
and it would simulate the resulting bright spots,
shadows, and reflections.
Global Illumination became the default lighting system
for every Pixar movie, making Pixar's light
more closely resemble the kind we see in real life.
But this model didn't account
for more fantastical scenarios,
like we'd see in "Inside Out."
Joy, the main character of "Inside Out,"
is supposed to resemble a star.
She's made up of glowing particles
that radiate off her skin.
This character had to shed warm yellow-blue light
wherever she appeared in a scene,
and the light had to track with her bouncy movement,
which wasn't easy, since she's literally a ball of energy.
So Pixar's RenderMan team came up with an effect
they called geometric area lights, or geolight.
This tool allowed lighting artists
to select a character model
and turn it into a mobile light source.
That way, Joy's light could travel with her.
If she walks up to a prop, she projects her glow on it,
and she casts light onto other characters, too,
like this pivotal scene with Sadness.
Her light was also accurate to her body structure.
For example, when she picks something up,
we see the light emanate through her fingers.
This made the outward glow look more believable,
taking Pixar's lighting system yet another step forward.
Nature plays a bigger role in "The Good Dinosaur"
than in any other Pixar film,
so the filmmakers really needed to nail the landscape
of the American Northwest.
They were especially focused
on the huge, constantly changing clouds
they observed on a research trip.
Traditionally, Pixar movies used matte-painted clouds,
meaning the artist would paint clouds
onto background plates.
But "The Good Dinosaur" took place entirely outside,
with clouds in almost every scene.
So they decided for the first time
to create entirely volumetric clouds.
That meant these clouds were 3D objects
animators could move around,
like a character or a key set piece.
But unlike a character or set,
a volumetric object has no defined surface.
It's just made up of billions of tiny particles.
The clouds team built a huge library
of what they called "cloud Lego parts."
They joined these volumetric forms together
to create huge clouds of every type:
rain clouds, stratus clouds, and cumulus clouds.
With the clouds actually in the scene,
viewers can move in and around the 3D forms
as the camera moves,
making this world that much more immersive.
Hank from "Finding Dory" was "probably the hardest thing"
Pixar had ever animated at that point,
according to Michael Stocker,
the supervising animator on the film.
He definitely wouldn't have been possible in "Finding Nemo."
Most four- or two-legged characters, like humans,
have joints and defined limits to their movement,
but octopi don't have skeletons
or any clear structure to how they move.
To capture that extreme flexibility,
Pixar had to rethink its whole approach
to character construction.
This started with Hank's rig,
the basic puppet that animators use
to control the character's movement.
While humans have clearly defined elbows that bend,
Hank's elbow had to travel
down the length of his tentacle,
so Pixar's engineers developed a special rig
that used a cylinder as Hank's elbow
and relied on a special curve function
to dictate how that muscle should move.
This let animators stay faithful
to that key rolling motion of octopus tentacles.
The filmmakers also needed
the webbing between Hank's tentacles
to flatten and spread out with each movement,
so the character team created a new control
to set the depth of the webbing.
This helped give Hank the squishy-squashy motion
that you see here, and it allowed Pixar
to give life to its most complex character to date.
The filmmakers behind the third "Cars" movie
wanted to emphasize the aging details on hero characters,
like the older racer Louise Nash.
Any car's surface is composed of multiple layers:
metal flake paint with a clear coating,
car stickers, dirt, grime, and mud composited on top.
But traditionally, when Pixar showed an object
with detailed texture from a more distant shot,
all the little details would merge into a single pixel,
making the object's surface look too smooth.
So Pixar developed a technology
called bump roughness mapping,
which converts what looks like bumps up close
into surface roughness in farther-away shots.
Louise, for example,
keeps the texture of her clear-coat scratches,
even in medium and wide shots.
And this tech wasn't only applicable to "Cars."
Pixar could use the bump-roughness method
to preserve details on all kinds of 3D objects,
as we'll see for "Incredibles 2."
Clothing simulation was always going
to be a big undertaking in "Coco."
The movie demanded more cloth than any other Pixar feature,
and many scenes would involve a lot of movement.
On top of this,
the characters weren't just humans, but skeletons.
Bones have all these crevices
where clothes can bunch up and collide with each other,
creating too many collisions
for Pixar's simulator Fizt to handle.
So the studio spent three years
creating a new continuous collision detection program,
which helped the computer automatically resolve issues
like cloth bunching up around a skeleton's hand
or snagging on a bony knee.
Animators also digitally wrapped the skeletons' joints
with super-stretchy invisible material,
so that when the bones separated,
the pants would touch that invisible barrier
and not fall into the gaps.
This was a creative solution to a unique problem,
but it laid the groundwork
for even more advanced cloth simulation later on.
Fashion was also a big part of "The Incredibles,"
but in the first movie,
the characters' suits weren't actual clothing.
They were patterns shaded onto the characters' bodies,
which is why, in some shots,
the fabric behaves more like skin
and the Incredibles logo stretches out
in unrealistic ways.
For the second movie,
the filmmakers wanted their clothing to work better
with the extreme movements of characters like Elastigirl.
That began with constructing actual digital garments
that sat on top of the characters' skin,
like normal clothing.
The next key step
was manipulating UV coordinates on the clothes.
In "Incredibles 2," a tech called 3D UV-scaling
preserved the details of a cloth
when stretched or compressed.
Pixar also found a way to use bump roughness mapping,
the technology from "Cars 3,"
to keep very fine illuminated details intact,
even when Elastigirl extended her body to wild proportions.
That made it possible for Elastigirl
to get a brand-new suit, this iridescent unitard
that keeps its subtle shimmery texture
through all the hyper-flexible movements.
Compare that to this shot of Elastigirl stretching out
in the first "Incredibles."
The surface of her new suit
looks much more like actual fabric.
You can see how Pixar has stretched the limits
of what its cloth technology can do.
The fourth "Toy Story" brought up issues of scale,
thanks to all the scenes set in the antique store,
and thus all the toys.
There were over 10,000 antiques in this store,
and Pixar had to find a way to program each and every one
with varying levels of wear and tear.
Animators tackled this challenge
by assigning three different ages to the antiques:
fairly new, moderately aged, and extremely aged.
The computer than gave the items surface details
that fit those ages, from micro-scratches on china platters
to wear and tear on old rugs.
The ability to add detail to so many different objects
is what gave the world of "Toy Story 4"
its visual complexity and appeal.
Pixar has had its share of unique characters,
but Dad from "Onward" is made up of only a pair of legs.
The rest of his body is just stuffing
with a sweatshirt, vest, and gloves thrown over it,
which made it difficult to animate.
Dad's legs could be rigged and animated
like a traditional character,
using reference footage filmed in front of a green screen.
But his upper half had no skin or structure underneath it,
so it called for simulation, not animation, in many shots.
The arms, for example, just had to flop around,
a movement that's more believable when simulated.
So the filmmakers developed
a hybrid simulation-animation rig for Dad.
With this rig,
animators could manipulate Dad's lower half
like they usually would,
but the simulation team controlled
everything above the belt when needed.
The movement of Dad's stuffing
was based on a volumetric sim,
a simulation for something with volume,
while the clothes on top of the stuffing
were largely controlled with standard cloth simulation.
Pixar also improved the interaction
between volumetric sims and cloth sims
so that if you pushed on Dad's clothing,
the stuffing would get squished believably,
and vice versa, if you pushed on the stuffing,
the clothing would move out of the way.
The hybrid rig improved the relationship
between separate simulations, and ultimately,
it showed how simulation and animation could join forces
to create realistic movement on an unrealistic character.
Pixar needed to make its musician characters
play instruments, most notably Joe,
who had to go through the complicated, rapid motions
of playing the piano.
At first, the team tried to use simulation
to handle the interactions
between Joe's fingers and the keys,
relying on a collision system
like the one used for the cloth in "Coco."
But the collision system didn't work,
because Joe's fingers were too heavy
for the computer's piano keys.
So instead of simulating the movement,
character technical director Jason Davies
developed what he called a finger contact rig.
When one of Joe's fingers pushed down on a key,
the rig would calculate the correct angle
for the key to rotate,
so it looked like Joe was pushing it.
The modeling and rigging teams
also gave Joe's hand 292 controls,
including variables they'd never used before,
even adding a control for each tendon
to convey the tension in Joe's hand as he played.
This level of hand and wrist control made his performances
look passionate and convincing on screen,
with a level of realism that pushed the boundaries
of human movement in animation.
"Luca" is a coming-of-age story
about a sea monster who can transform into a human,
and the filmmakers needed to show this transformation
in a fluid way.
They also wanted to give animators the power
to dictate all the details of that change,
such as where the transformation begins
and the speed at which it happens.
Before, adjustments to those kinds of details
would have to go through animation,
then go to the effects team,
and only then would animators get to see
how it all looked after rendering.
But for "Luca," they created a transformation rig,
so animators could fine-tune
the different aspects of the change one by one
and see the result right there in front of them.
That way, they could perfectly time the transition
from the layers of changes in the human skin
to the flipping scales and octopus spots
in the sea-monster skin.
This was a new way
to streamline the whole production process
and put more artistic control in the hands of animators.
After all, Pixar views technology first and foremost
as a storytelling tool.
Whether creating a new kind of light
to better convey a character's emotions
or rethinking cloud models
to give audiences a stronger sense of place,
Pixar's technical innovations
have always served its stories first,
and that's the key to the studio's record
of creating both groundbreaking innovations
and beloved movies.