Wednesday, November 19, 2008

Reader’s Question: “Breaking the Joints” in 2D and 3D Animation?

Richard Williams' "Animator's Survival Kit" talks a lot about the topic of "breaking the joints." I'm wondering if this is a technique that is exclusive to 2D animation or if it is used in 3D animation as well?

If so, can you elaborate on how it is used and maybe provide some specific examples?


This question comes from Jason. Great question! Thanks for coming by the blog Jason!

Breaking of joints, also often called "Sequential breaking of joints," or "successive breaking of joints," is basically a way of looking at your body mechanics as though it were a chain of events, or a series of joints where each joint affects the joint beneath it (and/or above it).

The classic example of this is in looking at a blade of grass or a cracking whip, where you could imagine the blade of grass blowing in the wind as being made up of a bunch of tiny sections which affect and move each other. Same with the whip. You could think of the tip of the whip as the very end of a series of "sections" or "joints," that snake all the way back up through the whip, into the hand, the wrist, the forearm, the upper arm, the shoulder, the chest, down the spine, and all the way to the hips. The hips are probably originating the whip action, and it propagates upward and outward from there, building in force and power until the tip of that whip actually breaks the sound barrier and makes that loud cracking sound.

The "blade of grass blowing in the wind" works the same way our spine might work as we're riding a bucking horse or doing any one of a huge list of actions that would originate in our hips (the base of the "blade of grass") and move upward with each section or "joint," having overlapped timing and creating follow-through action.

This idea is essential to creating a strong sense of internal force in your body mechanics, as well as nice follow-through, strong arcs, anticipation, weight, etc. It's one of the most fundamental concepts of animation and affects any number of other animation principles, so it's definitely something to continue investigating!

Shawn :)

11 comments:

Jason Fittipaldi said...

Hey, thanks Shawn!

We've just been getting into that topic in our AM class, so I'm definitely much more clear on the idea (and importance) of it.

When I initially asked, I had thought Richard meant "breaking the joints" in a literal way. For example, showing arms in legs in impossible/unrealistic positions for the sake of making the animation look or read better.

I feel like a goof =D

kddubb said...

Hmmm. I wonder if there isn't a double entendre going on here??? I just finished the section on breaking the joints in the Animator's Survival Kit a few weeks ago and I think it's very plain that Jason isn't a goof as I also thought this and am not a goof ;) I don't think Richard's descriptions in the book fit with Shawn's description either though (although I don't have the book handy to double check for sure). Are we sure that there isn't some confusion here caused by similar terms by different people in the industry?

Maybe I am an even bigger goof for pushing back while being still very wrong though.

mattanimation said...

I agree with Kddub. I am no Mentor by any means, but Jasons comment is right, Richard does mention that the limbs do "look" like they are impossible shapes because they are, but just like Shawn mentioned about the cracking of a whip, on the frame just before the recoil the shape is pretty much the opposite, so it's the same concept, plus you won't really see that unrealistic frame cause your brain does the in-between.

P.S. we have to be goofs to learn! I am probably wrong too ;)

Philip Crow said...

Well, when I read the Animator's Survival Kit, I believe it covers both what the body naturally does and what the body can't do in animation. As Richard William states, animation is so great because we can invent. I know just sequential breaking joints in 3d is easier than to get the actual break of joints, when elbows and knees bend so far backward usually because it distorts the mesh.

Back the question, I try to use it in 3d but have to limit what can be done with the mesh. In the classic example of the fist pound, leading up with the elbow trailing the fist, then switching the elbow down and keep the fist going up, then the fist comes down. Anyways, for me, in 3d, the switch of the elbow in direction and keeping the hand is difficult to get that quick snap that makes it seem so flexible. It can be done, but I find it difficult to get it to look right, best to keep trying till it does look right or find a different solution to what you want to achieve.

Well, hope my perspective helps, anyways, rock on!

Phil

sketch seven said...

I'm fairly certain that when Richard William's is talking about breaking of joints, he means physically bending a leg in a direction that anatomically looks wrong – for example, bending a leg so that the knee looks like it's twisted in the wrong direction.

There is also something that's covered in the AM class on overlap (just in Class 1 right now actually) that deals with overlap, talking about the successive breaking of joints when animating something like a pendulum, but which could equally be applied to a tail or a spine.

So yeah - same term, but different things.

I think, unless your rig has been specifically designed to allow for the RW version of breaking joints, it simply wouldn't work - you'd get your character's geo twisting and breaking very badly.

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dennis e. sebastian said...

Hi Shawn, i'm not sure where to post questions so i hope it's ok to ask them here in the comments.

When using live reference, how do you stylize it or make it cartoony but still capture the essence of the original movement?

My problem is when i follow the live reference too closely it begins to look rotoscoped but when i exaggerate it becomes a different pose/movement altogether.

Nenad said...

Hey guys... saw this post and comments and thought I might drop in and try to clear up a few things...
Jason maybe wasn't specific enough in his question so Shawn understood that he asked about the 'successive breaking of joints' when in fact he was asking about the over-rotated knees, elbows etc.
I'm working in a non-English speaking industry so I don't know the correct term for what you asked, but I can surely give you an answer,
and in short, it's yes.
Definitely depending on the type of project you are working on - realistic cg film doubles won't have this technique used on them at all, whereas squashy toons prettymuch will.
I use that a lot when animating soft characters. You use whatever helps you achieve the look of the motion you want, and breaking (over-rotating) can give your poses much more flex.
You just have to be really careful so it's not (too) obvious : )

Hope this helps.
Cheers!
Nenad Mitrovic

Jason Fittipaldi said...

Thanks for all of the feedback!

It's pretty clear now that there are two meanings for the same animation term.

I think Nenad answered my original question, which was whether this technique of physically impossible poses was a relic of 2D animation or if we see it at all in 3D animation.

I need to frame-by-frame Horton and see if they have any of that in there, as that seems to be one of the more 2D-like styles I've seen in 3D animated films these days.

ashton said...
This comment has been removed by the author.
ashton said...

This seems to go against everything Richard Williams says. Clearly breaking joints means bending them in ways which are impossible. Subconsciously this makes the animation feel more realistic. It makes sense. Surely it's possible using switching between rigs?