Disney's Practical Guide to Path Tracing

How does Disney animation create such realistic images?

Have you enjoyed the beautiful imagery from Disney’s new animated films like Big Hero 6, Frozen, or Tangled? What makes them look so realistic and beautiful?

Unlike in traditional animation, where each frame is hand-drawn and painted, today’s CGI (Computer Generated Imagery) Animation is actually based on the physics of light, while still being controlled and styled by artists.

While the technology shown in the movie Big Hero 6 was amazing, the technology used to bring the film to life was equally impressive. From software like Tonic, originally developed for Rapunzel’s hair in Tangled, and used tremendously to illustrate Elsa’s character arc through her hair in Frozen; to Hyperion, a new renderer developed over two years while Big Hero 6 was in production (and named after the original location of Walt Disney Animation).

However, some of the imagery in Big Hero 6 was so complex that the team at Walt Disney Animation had to create new software just to handle it: Coda (named after Koda from Brother Bear, but with a computer ‘coding’ twist). What Coda does is create a 55,000 core Supercomputer out of render farms spread across 4 geographic locations!

To give you an idea of how powerful this supercomputer is, Disney’s Chief Technology Officer Andy Hendrickson says it “could render Tangled from scratch every 10 days.”

Why did the Disney artists need so much computing power to bring Big Hero 6 to the screens? This entertaining video from Walt Disney Animation Studios explains how their artists and technicians work together to create beautiful imagery. It’s a little bit technical, but entertaining enough to capture your attention. Who knows, this might inspire the next generation of artists and computer scientists!

If you’re interested in learning more about the art of character animation, then sign up for our free animation newsletter!

Ed Hooks Acting for Animators

The Illusion of Life and Acting

In an interesting Slate.com article  (“How Does a Pixar Film Get Made”, March 18, 2015), long-time Pixar layout artist Craig Good provides the studio’s definition of animation like this:

“The definition of animation used at Pixar is ‘to bring something to life.‘  If the audience is convinced that a character’s actions are the result of a thought process, then they will see that character as alive.”

Bringing a character to life is an essential first step for performance animation, but Pixar’s definition of animation does not come close to describing how acting works.  “To bring something to life” is what you do when endowing a character with  “the illusion of life”,  just as Frank Thomas and Ollie Johnston explained, in their essential book The Illusion of Life: Disney Animation on page 507:

“…each (character) thinking his own thoughts, and experiencing his own emotions.  That is what makes them so real, and that is what makes them so memorable.  It is also what gives them the astounding illusion of life.”

The Illusion of Life Isn’t Enough

Making a character seem “real” or “alive” is where acting begins, not where it ends.  When animating characters, it is important to remember that acting is doing something and that acting has structure.  A character can have an illusion of life, complete with thinking and vivid emotion, and still be boring.  Example: take a look at ths 3-minute compilation of clips from the Disney film Bolt, featuring Rhino the Hamster.

Most of the sequences display no acting at all, just cute anthropomorphic animals hanging out talking, talking, talking and talking some more.  Rhino exudes personality, energy and emotion; he is overflowing with the illusion of life.  The problem is that emotion is not actable.  Illusion of life is not enough.  The underlying challenge in these clips is that the script is weak. It’s a horribly over-written, dialogue-stuffed screenplay, and even Disney’s talented animators couldn’t save it.


Contrast the weak performance in the Bolt scene to the superb performance in the low-battery Baymax sequence from Big Hero 6.

Both characters – Hiro and Baymax – have been endowed with the illusion of life but, significantly, they are also doing something, namely trying to get Baymax plugged into a re-charging station.  In order for a sequence to be theatrically valid, a character should have a provable objective.  In this case, reaching the re-charging station is provable because the characters will know whether or not they got there.  A character should be playing actions in pursuit of an objective.  Hiro’s actions are to keep Baymax generally on track to the recharging station.  A theatrically valid sequence also requires conflictobstacle, something that the character must overcome in order to achieve his objective.  In this case, Baymax’s low-battery status provides plenty of that because he can barely stand up, let alone navigate home where the recharging station is.

I will depict hatred, but only to show that there is something more valuable.

I will depict a curse to show the joy of liberation from it.

I will depict the boy’s understanding of the girl and the process by which the girl opens her heart to the boy.

In the end, the girl will likely say to the boy: “I love you, Ashitaka.  But I cannot forgive humanity.”

Smiling, the boy will probably say: “That’s all right.  Let’s live together in peace.”

This is the kind of film I want to make.  

Princess Mononoke Planning Memo, Hayao Miyazaki

from his book Starting Point, 1979-1996  

Ed Hooks

Acting For Animators

Ed pioneered Acting for Animators in 1998 while working with the animators at PDI/DreamWorks in northern California. Since then he has presented his masterclass at most major animation studios and game companies internationally. Ed’s book Acting for Animators, now in it’s 3rd edition, is a required text for animators in training everywhere. Ed is a DeTao Master with the Beijing Masters Academy in China and a featured speaker at animation events around the world: FMX in Stuttgart, Germany, Animex in England, Siggraph, the Game Developers Convention and many more.

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Human Anatomy for Animators - drawings by kimsuyeong

Anatomy For Animators 01 – The Human Skeleton and Muscles

Most of us are taught anatomy in at least one class in school (mostly before the frog dissection). Out comes the plastic skeleton on his rickety little trolley base, grinning from ear to ear. But we never really truly remember (or use) the information. We never understand the true nature of basic human anatomy when we sit down to animate. Animators tend to be very much creatures of habit. Sadly if it’s not known, or if the information is not clear enough, (or doesn’t have any drawings) we tend to discard the knowledge faster than trying to animate a one legged horse.

The posts on my blog that have been the most popular have been about anatomy for animators; muscle and bone relationships, and how they apply to animation. For the last four years, I have been trying to merge these into an interesting format with pictures. So when DJ Nicke asked me to write articles for Animation Salvation, I couldn’t refuse!

Human Anatomy For Animators

A series of Articles Exploring Human Anatomy from the Perspective of Animators

The human skeleton is fascinating, since we are one of the very rare animals that stand upright (bipedal), yet we do not have a working tail to balance. Gravity is essentially an enemy to us.

We tend to be more efficient energy wise as we have arms to carry stuff and only two legs that need to be powered to walk. So we have a really interesting, gravity assisted way of walking; and running in a state of perpetual falling and catching ourselves on the next step.

Anatomy study Upper Arm by kimsuyeong

Ok, so now for the dry stuff:

There are six major functions that the human skeleton, the three that we need to know as animators: support, movement, protection (the others are as follows; storage, blood cell production and endocrine regulation). Just to freak you out a little, there are 206 bones on average in the adult human body (most of them in the hands and feet).

Actions of the relation of muscles and bone; we work on a pivot and hinge system bone wise with muscle being essentially a pulley system.

Skeletal muscles are often named after the following characteristics:

  •  Number of origins: Biceps, triceps, and quadriceps indicate two, three, and four origins.

  • Location of origin or insertion: The sternocleidomastoid names the sternum (“sterno”) and clavicle (“cleido”) as its origins and then the mastoid process of the temporal bone as insertion.

  • Location: In addition to its origin or insertion, a muscle name may indicate a nearby bone or body region.

  • Shape: The deltoid (triangular), trapezius (trapezoid) and rhomboideus major (rhomboid) muscles have names that describe their shapes.

  • Direction of muscle fibers: The terms rectus (parallel), transverse (perpendicular), and oblique (at an angle) refer to the direction of the muscle fibers with respect to the midline of the body.

  • Size: Maximus (largest), minimus (smallest), longus (longest), and brevis (shortest) are common suffixes added to muscle names.

  • Action: Terms such as flexor (flex the hinge joint), extensor (extend the hinge joint), abductor (away from the body), and adductor (return to the body) are added as prefixes to muscle names to indicate the kind of movement generated by the muscle.

Why should you take the
skeletal structure into account while animating?

It is the basic structure of any basic living creature and therefore it will only move in accordance to the hinges or the rotators that are put in place to allow the freedom of movement within the confines of gravity.

Ball & Socket Hip Joint

Ball and socket joints: rotate until constrained either by the pelvis or the shoulder blade and clavicle.

Knee Hinge xray

Hinge joints: arc until constrained by the particular end of the joint which locks into place and does not allow over movement.

Cervical Vertebrae

Vertebrae: held in place by sheaths of muscle, keeping the vertebrae in place while allowing the column to pivot.

 So one side is the pulley and the other side is the counter stretch.

Involuntary Muscles

  • Involuntary muscles are muscles that are not controllable consciously, and instead contract due to unconscious impulses sent by the autonomic nervous system or certain specialized cells or hormones.

  • Both smooth muscle and cardiac muscle can be classified as involuntary muscles.

  • Smooth muscle is comprised of spindle-shaped cells that have no striations and is found in numerous locations throughout the human body.

  • Cardiac muscle is striated rather than smooth, and is found only within the walls of the heart.

Skeletal Muscles

Everything else is comprised by what is called skeletal muscle and they are like giant rubber bands with the elastic bands running in what ever direction they need to contract in. So you know when you have stray threads in a piece of clothing? And you pull it and the rest of the fibers get bunched up? That is exactly how muscles work, if they just contracted like rubber bands we would never get them back to a semi normal state.

I have found in observation that
people tend to favor one side of their body in movement

So that side tends to be more developed than the opposite. This tends to mean one side is a little shorter (not by much). You should make sure that you take this into account when capturing life action movement.

Have you played watchdogs (the video game)? If you look closely, (and I had to point this out to a non animator friend of mine) you can see that the run cycle isn’t even. Since it’s all mo capped, the non dominant foot stays on the ground longer than the other, leading to the run cycle cutting off the end of the animation. This results in a very funny non limp in the run cycle. Here is a video where you can see this for yourself:


This concludes our first lesson in Human Anatomy for Animators. Now that we understand how the skeleton and muscles affect the movement of the human body, we can look at those movements in more detail.

Human Anatomy for Animators - drawings by kimsuyeong

Anatomy For Animators 02 – Anatomical Movement

The body is interesting, even in a resting state, as the body doesn’t ever truly stop. There are always subtle movements: shifts of weight, breathing, the unconscious balancing act, conscious feedback of where our limbs are at any given moment, blinking, and thought.

We are going to start with Breathing

To understand breathing, you have to know that gases travel from areas of higher pressure to areas of lower pressure.

Intercostal muscles of the lungs and ribs
  • In the first stage of inspiration (breathing in): the diaphragm contracts and moves down and the intercostals contract. That means the rib cage rises and expands outwards where the diaphragm contracts. The larger volume in the lungs means lower pressure and the air flows in.

  • In expiration (breathing out): the diaphragm and intercostals relax so the rib cage shrinks back to a normal state. This returns the pressure to normal and the air that has been breathed in gets expelled as the lungs return to a normal state.

Intercostal muscles of the lungs and ribs, with Diaphragm

Let’s Move Our Anatomy!

What about movement and locomotion? In order to move, the body has to go from a rested state into movement. That’s when we need to know the four contraction states of muscle. Skeletal muscles are the ones that really concern us and are the muscles that cover the entire skeleton. Without them we could not move and they make up around 50% of our body weight:

  • In concentric contraction, the force generated is sufficient to overcome the resistance, and the muscle shortens as it contracts. This is what most people think of as a muscle contraction.

  • In eccentric contraction, the force generated is insufficient to overcome the external load on the muscle and the muscle fibers lengthen as they contract. An eccentric contraction is used as a means of decelerating a body part or object, or lowering a load gently rather than letting it drop.

  • In isometric contraction, the muscle remains the same length. An example would be holding an object up without moving it; the muscular force precisely matches the load, and no movement results.

  • In isotonic contraction, the tension in the muscle remains constant despite a change in muscle length. This can occur only when a muscle’s maximal force of contraction exceeds the total load on the muscle

We have to be observers and notice things that most people never notice.

As animators we need to observe and pay attention to the movement when there is no movement. We need to observe the distinction between conscious movement, unconscious movement, and movement caused by our anatomy.

Muscles contracting involuntarily, trembling of limbs, air forcing the lungs to expand and contract, the blood pressure in arteries moving the fingers – when we are still our bodies are not, the autonomic systems in place make sure that we stay alive.

The lungs increase in volume, breathing quickens, eyes start moving faster as they blink in anticipation and start focusing where the body will be moving to, muscles contract as the brain informs them that the body will be moving – This is not just for the preparation of an Olympic sprint, but even for the body simply getting out of the chair or starting to walk.

The muscles start contracting from the origin of the moment i.e. the muscles around clavicle and the shoulder drive the action of throwing the ball, the elbow starts engaging as the muscles in the upper arm pull the the hinge up, the tendons start pulling fingers tight around the ball as the they start contracting from their origin behind the elbow, the muscles above shoulder and the clavicle engage even more to pull the the arm straight up. The body has started to slow the breathing as the blood starts flowing faster with the oxygen rich blood, the heart starts to beat quicker to keep up the supply to the muscles that are working. The eyes hold the gaze as the body gets more focused in the activity. Then the muscles engage to throw.

The muscles tremble and spasm slightly as they stop contracting – they have done their job, performed the task that they were asked to by the brain. The body slowly returns to normal heart beat rhythm as the lungs return to the normal breathing rate. The muscles in the face might twitch slightly as the eyes track movement of the ball waiting the indication to move the body into a emotional state depending what the ball does.

Weight, Mass, Momentum

Though it would be interesting to talk about how muscle mass affects the body, now in animation terms you say that mass=weight, and if there is a heavier (i.e. ogre) model it walks slower… right? In real life it is not so straightforward.

Let’s take for example a man with big muscles; he appears to walk slow, right? If we could see his muscles underneath his skin, they are in a contracted state. Muscle contraction happens all the time, but exercise can cause a muscle to stay in its contracted (shortened) state. When it is like this, a muscle will not move freely from contracted to a relaxed state. It looks like the man is stiff in his stride because that is what is happening; the muscles don’t relax and stretch away from the body. That is why he is walking slower; he is more bulky, so the mass is more than the weight in this instance, as muscle weighs more than fat.

What happens if muscle stays in a contracted state? The muscle then stays in a shortened state resulting in loss of range of motion for that particular muscle and can result in changing the way that the body can move.

The man with more fat than muscle has to swing his arms further and moves the torso quicker to get the momentum up to walk. His legs are always trying to catch up underneath the body in smaller steps than normal. The short steps are trying to balance the body mass more than a person of a smaller size. People that carry more weight don’t actually have less muscle, as you might think. They have to carry more weight with every step. It seems like the fat man is walking rather fast; which he is. It is just taking him longer to get anywhere. He needs to expend more energy with each action, mass=weight with the weight of fat being more than the weight of muscle on this person.

The skinny man seems quite fast in movement to the others. He has no real mass (muscle or fat) and is quite skinny. It doesn’t take him long to move as the mass is not constraining his movement as much. Take note of this: if for any reason the muscle outweighs the fat or vice versa, the action would be slower as the muscle has to move the fat and the fat breaks down to feed muscle so therefore the skinnier guy would have a harder time moving if these weren’t equal.

You are probably to the point in your animating that you have have the idea down that timing of the movement has to originate from the torso when moving… legs, arms, torso and the head have to take their direction from driving forces, thinking and balance as well as gravity and physics.

But have you thought that because things weigh more in the body that they will take more time to respond to the movement and the force of the action? Swing your arm around.. and notice that the heavier upper arm even though the movement originates from shoulder will have different timing and different response to the force of movement compared to your very light hand.

Anatomical Animation and Movement

Hopefully that gives you a solid foundation of anatomy for your animation, and an understanding of how your anatomy affects the way you move.

In our next article, we are going to look at the anatomy of walking.

The Making of Cursed, a Juba Polati Animation Tutorial

The Making of Cursed – Animation Workflow Tutorial

Hello there, my name is Juba Polati and I am the animator who created “Cursed” – that short film where a bunch of stuff happens in Maya, yes the one with the T-Rex. If by any chance you haven’t seen it, I would love for you to watch it, it will make things a lot easier to understand from now on.

The Animation Process

Before we begin, I want to clarify that there are many ways to create a project, here I will briefly talk about how I tackled my Short film, just bear in mind it isn’t the only way. Also, I will be using a lot of terms and words that are part of the CG and Animation world, I will try to explain as much as possible, but if you don’t know a specific word, then it’s a great way to familiarize yourself, look it up online and find out what it means.

My process is a lot like what DJ teaches here at Animation Salvation, but still, a little different, here I’ll explain. These are what I would call my steps in regard to DJ’s.

  1. Foundation – Research/Pre-Production
  2. Structure – Production/ Golden Poses
  3. Details – Blocking/ Splining
  4. Polish – Splining/ Polish

With that being said let’s begin, but first Research!

The Research

After I came up with the idea, which is the easy part by the way, I went and did some research! What I mean by that is, I thought about what I wanted the film to be, so I went online to find images that had the same look, and same style I was going for. I tried to find things that would help define what I wanted to create, so the transition of what’s going on inside my head to reality was as close as possible.


On the other hand I also needed to find out how I was going to make it. My first major road block was figuring out a way to have everything inside a Maya scene. I started experimenting with screen capturing & practicing the mouse movements to fit the action of the character; but I soon realized that would take more time than I had. So I figured out another way to approach it, I would “fake” the scene, by measuring the width and height of the Maya UI (User Interface) and creating a 1:1 plane in the scene I was able to project the texture of the UI onto it. I then created a simple rig to control the interaction with the mouse and there it was, the basis of the project. I maintained the same idea for everything else, creating other planes with projected textures for the file menu and Import screens, and a simple 3D rig for the Cursor.

That let me have absolute control over the timing and interactions, which in the end saved me a lot of time. After figuring that out, I could actually start planning the film, and move on to the animatic.

The Animatic

For those of you who don’t know what an animatic is; it is the simplest form of showing your animation or movie. You make storyboards and compile them to show the pacing and timing of your shots. Create an animatic! It becomes incredibly easy to tell what works and what doesn’t in your film, and so, easy to fix at this stage. Watch these clips, they will explain it a lot better than I can.

What is an animatic?

Avatar Animatic:

I can definitely say this was the hardest part for me, since the idea I had let me explore several different situations, and it was hard to pin down the story and interactions to fit the short time frame I had. But with this process I was able to figure out what story I was telling and how I would tell it.

For me it was easier to go straight into a 3D animatic since my staging was incredibly simple and I didn’t have any complex compositions. So I shot some live reference of me playing out what I imagined the interactions would be like, cut and edit my footage to play like the film and added most of my golden poses to the scene, and there it was, I had my 3D animatic. I make it sound simple but this stage took weeks of work and planning, and the contents of the film changed several times.

Looking back now and seeing how much the final product changed from my initial idea, boggles my mind, but I was aware of every change along the way

and knew I was changing it for the better. I have to say I had a lot of support from my animation teachers and friends, and without them, the film wouldn’t be half what it is. So in this stage, show your stuff to other people and ask them what they think. It really helps to have that different perspective.

At this stage it’s all about experimenting, creating, showing, reiterating… Rinse and repeat. And after you have something that works and that you like, well then my friend, it’s time to get your hands dirty!

Animation Production

Animate, animate and ANIMATE! That is all.

Well there is a bit more to it than just saying animate… In my case I had a huge scene (time wise, not in actual file size) that held all my golden poses, but if I started animating within that scene, for one it would become really heavy and give me immense heartache at the end of production, and lastly I would never feel like I was accomplishing anything, since the shot would never be done until the last moment. So I got some great advice from my mentor to break the movie down into separate shots, that way it would become a lot more manageable, and by separating them into difficulty, from easy to hard, it became easier to judge how much work I had to do.

I started with the easiest shot I had, to get the animation juices pumping to my brain, and immediately jumped to one of the hardest, I made it my priority to finish the hardest ones first, because leaving them to last was too much of a risk. I would always go from a hard shot to a medium, back to a hard and then maybe an easy one to regain my spirits.

But you must be asking: how do you take on a shot?

Taking on a shot

Where to start? A lot of places, first and foremost, on your computer desk. Sitting with the correct posture, and also taking breaks every hour to stretch, because kids, maintaining your physical health also keeps your animation “alive”, see what I did there? I mostly start on paper, writing down my character motivations and actions I imagine would happen in the shot, and with that in mind I move on to shooting live reference.

Reference is incredibly important to your shot and Animation in general, so I focused on learning a lot of the process and how to make it work for me. I would get a camera that shot in 24fps, go inside a room and stay there for hours at a time, thinking of silhouette and staging, character reactions and motivations. I had a lot of help from my friends, but if you’re not comfortable with shooting in front of other people, that’s totally fine. Find what works for you.

After I got my reference, I would cut and edit the shots I thought worked best, and mash them together into a single clip. That made analyzing and studying my body acting a lot easier. I analyzed the clip to understand what was moving when, and where the center of gravity was; all that good stuff.

Golden Poses

These are the most important poses in your shot, with only Golden poses, you should be able to tell exactly what’s going on in the shot. I would find what my main poses were and time them to my reference. That way I could work really hard to make them shine! Like they are made out of gold, because gold is shiny, and they are the “Golden” Poses… That worked better in my head…

Blocking Your Animation

After I had my Golden Poses, I would block in the key poses to tell the timing, extremes and movement in the shot. Keep in mind in this phase I’m still in stepped mode, working to find the right timing and spacing in my action.


After I was happy with my blocking, I would start adding breakdown poses, to help define my arcs, overlapping actions and follow through. This helps to read the action better and get a better sense of the movement.


Splining Your Animation

This is the part where you take your animation from Stepped mode, into the smooth Linear, or Auto mode. I experimented a lot in this phase, changing the modes to see what I preferred for the shot. This is also the part where I started to clean up my Graph Editor.

Polish That Animation

This is the last 10% of your animation, the cherry on top! I spent a lot of time in this part, just adding detail and texture to the animation, but one thing I always kept in mind is knowing when to be done with a shot and move on, since I had another fourteen to work on. It is hard, and a lot of times I left a shot with the feeling of it not being done, but that let me touch every shot then go back, polish and fix what I already had.

In this clip Jeff Gabor masterfully shows all these processes at work:

What did I do after I finished animating? Ha! Surely you jest my friend! I was never done animating! I had a deadline, and so couldn’t animate anymore =D. But either way, what about rendering?

Post Production

Rendering is for FOOLS! No, I joke. Rendering is awesome! But I had a choice: spend time rendering or animating? I chose the latter and playblasted my film. I just found a way to get a decent quality out of the playblast and since I was doing that anyway to check my animation, I had all my shots getting updated every time I polished something.

All I had to do was some editing, titles and picking my soundtrack, which I did from 5 Alarm. The Sound Design was done by Matt Thomas from VFS. Thank you to him!

Final Words

Well this was mostly my process, and there were times where a lot of these overlapped each other in production time, I was editing and doing titles, while I animated, I was blocking a shot and polishing another. Also what I describe was a process taught to me by incredible artists (aka animation Teachers and friends) that supported and helped me through making the film, so for that I’m always grateful. If you made it this far I congratulate you on the conviction and thank you for reading! Now, all I can say is, go animate!

Cursed | Animation Tutorial