21 November 2010

Some Talk on Organic Motion

The Organic Graph

What is an Organic Motion, Movement ? The simple way to describe it would be in opposition to a very robotic or mechanical movement. A movement that would not contain any Overlapping Action, Slow-In / Slow-Out, Arc and Opposite Actions as the video example below. So that Organic Motion refer to a natural movements, a movements from living things as human who are generally moving in an organic way.

Overlapping Action

The principle of Overlapping Action is the decomposition of the movement so that not everything in or on a character starts and arrives at the same time. It could be understood in opposition to a basic interpolation, where everything would move at the same time between poses.

In a character, two possibilities:

First, Overlapping Action means varying the timing within a hierarchy of connected parts as the arm, forearm, and hand for instance to get some follow-through (so that something is leading and some things are dragging).

Secondly, Overlapping Action means advancing and delaying various body parts as they arrive at their final position, as long as these parts work organically and logically.

Eric Goldberg p.101

On a character: Inanimate objects that are usually slave of the primary action. Things like earing, hair, clothes, appendage or a cartoony tail for instance, won’t hit the same timing as what is leading them.  

In other words, it means that thing move in part. That one section of the body goes first, and another section of the body goes after until all part of the body has come to the next pose. Each parts overlapping their timing or doing a little pause before the other parts start to move (or the combination of the two). 
*See Richard William, The Animator’s Survival Kit p.226 to 230 and The Animator's Survival Kit – Animated; disk 9 

It’s this overlap of different section of the body between poses that will give the illusion that a second action is starting before the first action has completely finished, thus creating more organic and believable actions by establishing relationship between them.

Follow-Through (or Lead & Drag / Lead & Follow)
Follow-Through, which is a subtext of Overlapping Action, simply means that some parts of the body will Lead an action and some parts will Follow an action, as these parts were listening to what’s pulling them, but with a delay. It happens because we are not a rigid figurine, but a body compose of mobile parts with their own inertia. 
To understand Follow-Through it is important to understand what it encompasses:
What it encompass:

•    One part Lead. And that part will lead in a certain direction: Direction of Thrust.
•    Some parts Drag, which will be delay behind the leading part because of their Inertia. 
•    The Follow-Through happen when what’s leading stop or change direction, the parts that drag will continue to move due to their momentum.
•    Overlap : The zone where 2 drawing will make contact, will be over the top of each other, will overlap each other’s. So that the more your drawings overlap, the smoother your action will look. When a hierarchy of joint unfold with leading and dragging parts, the overlap in the drawing will make the action smoother and easily understandable. 

Also, are we leading with the top or the bottom  ?

•    Progressive : If you are leading with the top of the hierarchy (see the video examples below, a snake for instance would lead progressively with his head)
•    Digressive: If you are leading with the bottom of a hierarchy, which is what we are normally doing.

Sometime, follow-through is seen and explains in term of D, S, C (or C minus) shape, or in term of section of a wave that represent these three shape. For instance, suppose that you have a moving block with a pendulum attach to it (as with the Animation Mentor exercise). As the block move right the pendulum drag and form a D shape. When the block stops or change direction, the pendulum’s D shape becomes an S shape because the upper section of the chain lead and the bottom drag. And finally, the pendulum’s follow-though will transform the S shape in a C shape before coming back and repeating the pattern until it stop. If the “S” wasn’t here, there would be no sensation of weight, of thing being dragged.

Sorry for the Dirt !

So really, follow-through simply means that things won’t move at the same time within a hierarchy as one part is leading and others parts are dragging behind. And because it encompasses the concept of timing, that thing doesn’t move at the same time, it can be viewed as a subtext of Overlapping Action.  

Follow-Through: A subtext of Overlapping Action

As we said, Follow-Through is as a subtext of Overlapping Action, because as in Overlapping Action, in Follow-Through things won’t move at the same time as one part lead and others parts drags. But Overlapping Action is not necessarily Follow-Through. Because Follow-Through apply to one hierarchy of joints where something lead and some things drag as Overlapping action encompass body part that are not necessarily connected to each other’s (not in the same hierarchy). 

For instance, for Overlapping Action you could have the front foot during a baseball pitch that starts to move before the body or one foot leading during a jump as the other foot lag behind. But in these two examples, because one foot is not “connected” to the other foot there is nothing really leading or dragging (as in Follow-Through), it is just that one foot move on a different timing, even if in the jump the foot that goes last, come last so that we kept a logical order in the movement. 

Successive Breaking of Joints:
 “The term first coined by animator Art Babbit to describe how a character move fluidly based on anatomy.” –Eric Goldberg p.XXI
Successive Breaking of Joints means that instead of having the joints in a hierarchies move at the same time from one position to the next. Having the joints break successively from the source of the action or force will show flexibility, weight and deployment of force.

In animation, the concept of Successive Breaking of Joints is use to describe how a character move fluidly based on anatomy, as Eric Goldberg points out. It could be seen in opposition to rubber hose animation where limb of the character had fluid movement, but with no bone structure.

Eric Goldberg p.43

It’s interesting to note that in Biomechanics, the concept of “breaking the joints successively” haves a specific use in physical skills that require high linear velocity on the end of the segmental link system (i.e. high baseball speed in a baseball pitch (can attain up to 170 km/h),  contact foot in kicking, tip of the sword in a sword strike). It’s known as the Kinetic Link Principle, where there is a sequencing segmental rotation of the joints. Just as the tip of the whip can be made to travel so fast that it has a supersonic speed (hence the sonic boom heard as the crack), the small segments of the hand or foot can be made to travel extremely fast by sequential rotation of the body segments, because the rotational inertia of the system become progressively less through the body’s segment.

Successive Breaking of Joints: A subtext of Follow-Through
Successive Breaking of Joints is an essential idea in creating nice follow-through, if you are animating something with joints. It can be apply to broad action as in a baseball pitch or someone riding a horse bucking, or it can be apply in subtle action like in a hand clap. So whenever you have some follow-though where something is leading and dragging, the idea of breaking the joints successively will be underneath it if you animate something with joints.    

Tools for weight in animation: Follow-Through and S.B of Joints

If a force is applied to an object, it will accelerate progressively by slowing-out in the direction of the force, because it has inertia. That’s where we feel the weight. If some parts attach to this object lag behind, it will do so because it has inertia, and will continue to move (will follow-through) if the object stop because it has momentum. Again, that’s where we feel the weight, when something with or without joints is being drag and then follow-through.

We should note that Timing and Posing are the most important thing to show weight, as timing gives meaning to movement. If your timing is not correct, your animation could feel “floaty”, “watery”, “swimmy”, as it is submerged in an invisible pool of water. If you don’t have any Overlapping Action, your animation will certainly feel stiff, but without proper timing, adding whatever amount of follow-through/S.B of Joints won’t solve the problem.  

On this subject, here is a little quote from Keith Lango that I had found interesting (from this article): 

"We can see forces in a second hand fashion- by the force's effect against resistance. What kinds of resistance are there? The primary types of resistance are inertia and momentum"

Slow-Out / Slow-In

Every objects have inertia, which is the tendency of an object to resist any change in it's motion. Inertia if proportinal to the mass of an object. So that every objects needs to slow-out (accelerate) and slow-in (decelerate) when  they move or change direction. If they don't slow-out and slow-in it will look mechanical, unatural, inorganic.

Arc : 
*Here I have just copy paste the text from this page.
Arcs bring life to a movement, thus avoiding a mechanical look. Almost everything in the natural world moves in arcs. There are two major reasons for this:
1: Rotational Joints 

Your body is made up of a series of rotational joints, so when you move your body, it’s actually the result of your various limbs rotating around your joints. Because of this, our movements tend to follow arcs.  A human walk cycle is full of arcs. The body moves up and down, as well as moving forward, tracing an arc through the air:
2: Gravity 

Gravity also causes objects to move along Arcs. Take the example of the bouncing ball. If you throw it forward, it is also pushed down by gravity, making it move in an arc.
The main lesson to learn from "Arcs" is to try and avoid having any truly linear motion in your animation unless it is mechanical. 

Opposite Action:    

Here's the thing, during one of the Jason Ryan Webinar, I had lift my hand off and ask him this question : “How does opposite action are related to an organic feel in our animation”.  If you would like to hear his interesting answer, you need to buy the webinar series 2 on IAnimate (it’s only 100 $ for 12 video), and check the one from July at 1:59:10…

"Just that simple idea, of moving thing in two different directions make it feel better, that's why I say it make it feel more organic"

And here it ends

To conclude, Organic Motion can be understood in oposition to a mechanical or robotic motion and emcompass a few different things. First off,
we have seen that Overlapping Action really mean that things move at different time, that things start and stop at different time. We have seen that Follow-Through (or Lead & Drag) means that some parts of the body will Lead an action and some parts will Follow an action and that it can be seen as a subtext of Overlapping Action since what’s leading and dragging won’t move at the same time. We have also seen that S.B of Joints is a subtext of Follow-Through as it encompass the same notion that something is leading and some things are dragging, but now with joints. Then we have seen how Follow-Through and S.B of Joints contribute to the visual presentation of weight by showing inertia and momentum of objects. And finally we have seen that Slow-In / Slow-Out,  Arc and Opposite Action also contribute to give an organic feel to our animation.


Robert_(RKL) said...

Nice post with a lot of good example
you did your homework well. Qu'est ce qu'on ferait sans FRancis :)

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