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The Principles of A:M

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Starting this topic in order to explore the Principles of Animation as they apply to A:M.

The thought being that it may not only be interesting but might satisfy curiosity and make the specific referencing of the principles unnecessary in the revised TaoA:M.


The idea is to explore methods that can be used in A:M to reproduce or demonstrate the basic Principles of Animation.

Of course the number of principles does vary depending on who you reference so we'll start with something of an itemization.


On page 29 of current TaoA:M is the list "The 10 Animation Ingredients (Updated for Computers) as follows:


1. Pose to Pose

2. Anticipation and Overshoot

3. Follow Through

4. Exaggeration

5. Timing

6. Balance and Weight

7. Secondary Action

8. Attitude

9. Staging

10. Squash and Stretch


The terminology here is not accidental. Selecting from these ingredients helps to formulate a recipe that will flavor an animation to increase it's appeal and anticipate how it will go down with an audience. If successful the viewer will thoroughly enjoy the production and may even be entertained. These ingredients are adapted from the Principle of Animation identified (in part) by Disney animators who had perfected the craft of hand drawn animation in the 30's and 40's. In their celebrated book "The Illusion of Life" authors/animators Frank Thomas and Ollie Johnston listed 'The 12 Principles of Animation' as follows:


1. Squash and stretch

2. Anticipation

3. Staging

4. Straight ahead action and pose to pose

5. Follow through and overlapping action

6. Slow in and slow out

7. Arcs

8. Secondary action

9. Timing

10. Exaggeration

11. Solid drawing

12. Appeal


These are of course the same general principle John Lasseter applied to his work when developing computer animation with PIXAR. The real challenge was in how to apply these principles of classical animation to a new set of tools on the computer. He said, "Many of the principles of traditional animation were developed in the 1930's at the Walt Disney studios. These principles were developed to make animation, especially character animation, more realistic and entertaining. These principles can and should be applied to 3D computer animation." Twenty years later as head of Disney Animation and of PIXAR he's not only continues to apply these principles but expand and improve upon the tools that storytellers use. Here then is Lasseter's list of principles he'd learned first hand from Thomas and Johnston at Disney. His thesis published a mere seven years after the release of their book:


Principles of Traditional Animation Applied to 3D Computer Animation

1. Squash and Stretch - defining the rigidity and mass of an object by distorting its shape during an action

2. Timing and Motion - spacing actions to define the weight and size of objects and the personality of characters

3. Anticipation - the preparation for an action

4. Staging - presenting an idea so that it is unmistakably clear

5. Follow Through and Overlapping Action - the termination of an action and establishing its relationship to the next action

6. Straight Ahead Action and Pose-to-Pose Action - The two contrasting approaches to the creation of movement

7. Slow In and Out - the spacing of the in-between frames to achieve subtlety of timing and movement

8. Arcs - the visual path of action for natural movement

9. Exaggeration - Accentuating the essence of an idea via the design and the action

10. Secondary Action - the action of an object resulting from another action

11. Appeal - creating a design or an action that the audience enjoys watching

Personality in character animation is the goal of all of the above.


Everyone seems to have a favorite flavor and I would like to suggest the missing 12th principle from Lasseter's list is one of the secrets to his success in computer animation; solid drawing. We'll have to explore that element more at a later time but for now consider what the word 'drawing' actually means; it is not just the act putting lines and forms on paper but a process of pulling in, the art of illustrating... referencing.


People love to create lists and when it comes to the principles of animation a lot of other lists have been made. I believe it was Walt Stanchfield (Disney animator and teacher) who compiled a list of 28 principles:


28 Principles of Animation

-Pose and Mood

-Shape and Form


-Model or Character


-Line and Silhouette

-Action and Reaction







-Squash and Stretch

-Beat and Rhythm

-Depth and Volume

-Overlap and Follow Thru


-Working from extreme to extreme

-Straights and Curves

-Primary and Secondary Action

-Staging and Composition






-Positive and Negative Shapes


Someone else complied a list of 48 principles and I'd swear I saw one listing 110! Regardless of the listing you could compile, what will be most important is what these words mean to you and what begins to happen as you apply them.

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I wish it were as easy to teach them as to list them! Things like "weight" are simple in description but difficult in execution.


"Secondary Action" is the term that seems to have the most lack of agreement on what it refers to.

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"Secondary Action" is the term that seems to have the most lack of agreement on what it refers to


It seems straight forward enough.

Perhaps people confuse it with Follow Through? (I don't see how many would confuse it with Anticipation)


It may be an oversimplification but as a working definition I would suggest that Secondary Action is: "any Action other than the Primary Action" or "anything that supports the main movement, motion or activity" In this way we essentially prime and ready all Secondary Actions to act in accordance with Newton's Three Laws of Motion as the Primary Action is doing already:


First Law

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.


Second Law (Acceleration and force are vectors and in this law the direction of both vectors are the same.)

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.


Third Law (Perhaps the best known and most often quoted of the three)

III. For every action there is an equal and opposite reaction.


I'll propose this as a general rule for Secondary Actions:

While considering composition and layout, strive to keep Secondary Actions from taking attention off of the Primary Action (Focus) of the Scene. Consider how Secondary Actions can support, enhance and augment the main purpose or theme. Extra tidbit for free: Think of how Secondary Actions may be exploited in the course of subsequent viewings to reveal undercurrents, layered performances and deeper meanings.

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I used to hear Secondary Action defined variously as overlap or follow through but at animation school it was different.


Overlap is overlap, follow through is follow through, but Secondary Action is about an acting choice. It's what else you are doing while you do your main thing.


So maybe you happen to be chopping carrots while you are speaking your scripted lines. Or maybe you are mowing the lawn while you watch your neighbor.


The chopping carrots and lawn mowing are "secondary" to the story points of speaking lines or watching the neighbor but they help give the illusion of spontaneity that just standing and speaking or standing and looking would give.


That definition of Secondary Action falls with in "any Action other than the Primary Action" but is more specific about why we do it and why it is there.


Until AnimationMentor I hadn't heard Secondary Action defined that way.

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I should be sleeping but the idea of pressing further into the Principles of Animation with an emphasis on how to approach them in A:M is keeping my attention.


Overlap is overlap, follow through is follow through, but Secondary Action is about an acting choice. It's what else you are doing while you do your main thing.


This works for me. It reads like something out of an acting class which perhaps is where the whole Secondary Action idea stems from in the first place?


I found my copy of 'Illusion of Life' and read what they had say about Secondary Animation back in the 1980s. From what I've heard this 'lesson' is a favorite of most computer animators these days. The following except is from Page 64 (I'd quote more but at a point this starts getting ridiculous and it's better to just jump into A:M and start animating):


Sometimes the Secondary Action will be the expression itself. Suppose there was to be a change from a painful hurt to a helpless, bleak look as the character turns away, before he wipes a tear. The danger now is not that the expression will dominate the scene but that it never will be seen. The change must come before the move, or after, and must be staged so that it is obvious, even though of secondary importance. A change in the middle of a major move will go unnoticed, and any value intended will be lost.


(Interjection - I must admit this paragraph goes a little beyond my current understanding of Secondary Action and I'm adding it here to let it sink in more fully. The following paragraph is what will more obviously fit with computer animation because it has a more direct application. I need to return to that first paragraph and put into practice the idea there.)


One animator (Bill Tytla) found the proper relationships among all these parts through a "building block" technique. First he animated the most important move, making sure that it worked the way he wanted, communicating his thought in the strongest way. Then he went through the scene a second time animating the Secondary Action, and even once more if necessary, to make the rest of the drawing relate to those two actions. He continued to change and adjust until all parts of the drawing worked together in a very natural way.


It is advisable in any case to try it all in thumbnails - little exploratory sketches - before anything else, to make sure that everything will stage well and will look as convincing as the animator had hoped. When used correctly, Secondary Action will add richness to the scene, naturalness to the action, and a fuller dimension to the personality of the character.


This is nothing new to anyone who has been trying to animate for any length of time but it can't hurt to place it out front and center and present it confidently here. There are other ways to animate a scene but few will keep the focus on the Primary Action as much as animating the Primary Action first and then going back and refining the supporting detail on subsequent passes. It seems those old school animators were on to something there.


So, at any rate... that's an approach many would take to animating Secondary Action in A:M (most perhaps skipping the planning/thumbnailing stage). The methods used to get there would be Pose to Pose and/or Straight Ahead.


I'd love to hear how others approach Pose to Pose and Straight Ahead methods in their animation. Does anybody sketch first or thumbnail?

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Here's more follow up to the concept of Secondary Action. This one from the George Nash's write up for a Physics 211 course (back in 2002) entitled "The Physics Behind Basic Animation".




Secondary Action

There are two types of secondary action:


1. An action that is the result of another action.

2. Additional action aside from the primary action(s)


Secondary action helps add to realism. If you hit something it will move. This is the same concept as, "for every action there is an equal and opposite reaction". The reactionary actions must be shown to create a authentic scene.


Additional action aside from the primary action can be many things. It could be the waves in the ocean, that is in the background. An animator must be careful when adding in this type of secondary action because the eye is drawn toward movement and even the smallest movement can draw away form the primary subject.


San Jose State University and De Anza College are known for catering to the those with an interest in animation:



Here's a nice blog that has some interesting links to analysis of video and other physics related references. Apparently students analyze the physics in animated movies for part of their grade:



For all intents and purposes you can often study the same thing these students study online, you just won't have the instructor's interaction.


One of my favorite sites for online educational resources is MIT's OpenCourseware: http://ocw.mit.edu/courses/

I highly recommend the videos on Physics.


Lots of great stuff going on there at MIT. Let's say you want to animate a particular exercise such as a chin up... they've got a short video of it and other weight training routines there.


These can give you a nice beginning point to launch a search for other references.

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So, I hear you saying "But I want to be an animator NOT a physicist!"


One of the benefits to understanding the basic principles of animation is that they formulate shortcuts to more complex ideas that can be expanded upon. In execution it then becomes mostly a matter of extremes (degrees and extents). How far do you pursue realism and where do you prefer to leave off? Here we run smack dab into the Principles of Caricature and Exaggeration where we get to choose and extract those elements of realism and increase the focus on what we determine to be the most important parts.


Following one of the above links to the course on physics from San Jose State University will (eventually) reveal one approach to acceleration and deceleration that I find to be a good rule to follow. It can be quite useful in laying out a sequence or analyzing a shot you've already setup.


Acceleration: 1,3,5,7,11,13... n.

Deceleration: n...13, 11, 7, 5, 3, 1.

This, I believe, is referred to as the Rule of Odds. REF: Physics of Falling Part I (PDF File).


The useful thing about this methodology versus simply doubling up our numbers is how each instance is continually and incrementally sped up. The effect should, at least in theory, be more dynamic if not more effective on odds. Even increments, on the other hand, are rhythmic and repetitious, cyclic in nature, easier to predict and can be used to effectively calm an action down. This ratio is a means to effectively even out odd spacing into a less predictable yet useful and workable pattern. If the look appears to increase or decrease too rapidly one could always opt for doubling of the spacing from one instance to another; n... 2, 4, 6, 8, 10 etc., or halving the distance whenever slowing down.


One of the reasons I personally like this ratio in acceleration/deceleration is how it directly applies to classical animation with it's penchant for animating on 2s where every frame (or drawing) is presented to the camera twice rather than only once. Computer animation by it's very nature, unless specifically manipulated by the animator to be otherwise, will always be animated on 1s.


After the channels are reduced to the absolute minimum of keyframes this Ruling of Odds produces a (more or less) perfectly generic bouncing ball in both vertical and horizontal planes. In other words, the beginning frame and the ending frame positions can be changed and the middle contact point (inbetween) adjusts in space automatically. See attached movie for resulting animation with no squash and stretch:


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I had never heard of the rule of odds before! (I hope they are wise rulers.)

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SQUASH & STRETCH - Defining the rigidity and mass of an object by distorting its shape during an action.


TIMING - Spacing actions to define the weight and size of objects and the personality of characters.


ANTICIPATION - The preparation of an action.


STAGING - Presenting an idea so that it is unmistakably clear.


FOLLOW THROUGH & OVERLAPPING ACTION - The termination of an action & establishing its relationship to the next action.


STRAIGHT AHEAD ACTION & POSE TO POSE ACTION - The two contrasting approaching to the creation of movement.


SLOW IN & SLOW OUT - The spacing of the in-between frames to achieve subtely of timing and movement.


ARCS - The visual path of action for natural movement


EXAGGERATION - Accentuating the essence of an idea via the design and the action.


SECONDARY ACTION - The action of an object resulting from another action.


APPEAL - Creating a design or an action that the audience enjoys watching.


SOLID DRAWING - Natural and Appealing , not stiff poses.


(Source: Key to Keyframes)

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