For People Crazy About 2D Animation!

Acme Punched! is for people crazy about 2D animation. It may be enjoyed by beginners and others, but it is aimed at animators who know already something about the process of animation and the basics of character animation. In large part, it will attempt to provide a deep look into the problem solving that goes on in my head as I work out a scene, often in step-by-step posts that I will sometimes enter in "real time", without knowing in advance what the outcome will be. Mistakes and false starts will not only be included but emphasized, so that the creative process of animation will be portrayed realistically. And, while my own bias is for 2D drawn animation, many of the effects and principles discussed here can apply to CGI 3D animation as well. I hope the blog will prove useful and instructive for all.

-Jim Bradrick

Wednesday, June 4, 2014

No. 66, Creating a Four-legged Walk Cycle


A short while back ( Acme Punched posts No. 60 thru 62) I showed you my approach to creating a walk cycle for my character Albert.  Now here is a walk cycle, or rather a trot, for the little fox character.

First, a bit of re-design was in order.  I made the original model sheet without much attention to the real anatomy of a fox.  This is a cartoon and you can do that, but he does walk on all four feet so I have now decided it would be good to have him move something like a real fox, and for that, he has to be constructed a bit more like a real fox.

In the original model sheet, above, he is rather swaybacked and holds his tail erect.

The revised design makes his spine arc upward a little, as in real canines, and shows him holding his tail almost straight out behind him when moving.

 The Animation

Once again I wanted to try something I had read about but had never actually done: to animate the head, body and tail before doing the leg animation.  This is effective in animating dance and other controlled movement such as sword fighting.  Disney animators have used the technique in animating such semi-realistic creatures like deer (Bambi), though others actually did the reverse, animating the legs before the body. (I would cite a reference for that, but can't recall exactly where I read it.)

Anyway I thought it might work on my cycle of a fox trotting.


This was the first test.  It was made using just three drawings, with the middle drawing favoring the highest one in its spacing (see Fig. 1). I thought the rhythm was fine, but since the fox will sometimes be quite small on the screen, I decided it was too subtle.

Now for a broader movement, in which I simply let his body drop down farther.


At the time (we will come back to this) I thought it was fine, and went with it. Here is the spacing.

Then I was ready to add in the legs.  This is a basic canine trot.  I referenced a favorite but little-known book of mine: Dog Locomotion and Gait Analysis, by Curtis M. Brown.  Brown is not an animator but a dog breeder and dog show judge, but the sequential drawings of the gaits of various breeds are a gold mine for anyone interested in how dogs move.

Here is the test.

Hmm.  I sort of liked it when I saw it, but...something was not right.  Can you see what is wrong without reading further?

If you said that the head was moving too much, you would be right.  I had lowered the head along with the torso.  It is the same as it was in the second version without the legs (see Figure 2 again also), but somehow it was not apparent to me until I saw it all put together.

Solution?  Leave the torso as it is but just space the head much closer to the other heads.


Now it is working right.  Many animals avoid movement that bounces their heads up and down very much, because either they need steady vision for pursuit of prey or to detect danger.

One more thing I thought to do was to see if I could vary the speed--make him move faster--without removing any drawings.  (He may have to trot quickly to keep up with Albert's brisk walk.)  The slow speed is 8 drawings on 2's, or sixteen exposures, thus: 1, 1, 3, 3, 5, 5, 7, 7, 9, 9, 11, 11, 13, 13, 15, 15.  The numbers in bold are the lowest position.  The obvious thing to try here is to see if it will simply work on 1's: 1, 3, 5, 7, 9, 11, 13, 15.  But it looked too fast and also jerky, so I am not even showing it to you.  Although it does not always work to have some drawings of a walk cycle on 1's while others are on 2's, because of the danger of "slipping" against the steady movement of the background, I decided to try this: 1, 3, 3, 5, 5, 7, 9, 11,11, 13, 13 ,15.  In other words, I dropped the second exposure on drawings 1, 7, 9, and 15--just four frames fewer, but look at the result:


It seems to work!

Next: More about working with 4-legged characters!

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