3dflashworld

Motion Study

When I started this tutorial I was under the impression that I knew how a spider walked. I thought it was like any other
creepy crawly critter. Hour after hour I tweaked motion graphs trying to make my spider have a half way believable walk
cycle. I could never get it just right. It never looked convincing enough. I needed to see the real thing. This required that I
study the motion of a real life spider. There is no substitute for the real thing. The animator is the one who gives the image
life. We are the ones who ask the question, "Does this look right?" not the computer. In order to know what "looks right"
you have to study the motion of your subject. If it has a real life counterpart go look at it. The computer is a great tool, but
that’s all it is, a tool. Don’t get me wrong MAX has all the tools you need to make anything have a great walk cycle. Even
a plug-in as powerful as Character Studio only does so much. You have to give the animation life. This is one of the
reasons why animation houses don’t care if you know how to use the latest plug-in or not. They want to see if you have the
ability to animate, not use a mouse. One of the techniques used by animators is to study the real thing and try to capture the
essence of it in animation. Disney was known to bring in real life animals right into the studio for his animators to study.
So, as an example, let’s go through my motion study of a spider walk cycle. (Yes, I had a spider running across my desk.)

Don’t open MAX just yet. Instead get out a paper and pencil and do some sketches. Plan your animation. Don’t jump in
with all eight legs at once! Lets start by taking a look at some sketches I put together after observing my spider. The image
above is a concept sketch I made for modeling the spider’s leg. Though I am not going to go through how to model the
spider I included it here to emphasize the fact that we are dealing with a creature that has many joints. We are going to
simplify this by auto boning an existing linked mesh structure. This will greatly decrease the number of objects needed to
animate. So don’t be intimidated by the spiders complexity.

	Looking at the front leg first, notice that the spider reaches forward, places its foot and then "pulls" itself. This motion is much more exaggerated for the spider then for insects. Bugs "scurry," spiders crawl. I think that this "reaching and pulling" is where a large part of the creep factor comes in for the spider. Its important that we try to capture this quality. The "reach" is almost directly out in front of the spider.

Looking at the front leg first, notice that the spider reaches forward, places its foot and then "pulls" itself. This motion is
much more exaggerated for the spider then for insects. Bugs "scurry," spiders crawl. I think that this "reaching and pulling"
is where a large part of the creep factor comes in for the spider. Its important that we try to capture this quality. The "reach"
is almost directly out in front of the spider.

And the ;pull" brings us back to where we started. (It was difficult to illustrate, but realize that the body is being pulled forward equal to the stride length.) I noticed that each leg placement, especially the front legs, the motion is very deliberate. The spider is not just throwing its legs out there. The nasty knows where it wants to place its feet. Try to convey this deliberate motion with slower deliberate movements. Now lets look at the other front leg. It too is going through the same motion, but it’s off set in time by half of a cycle. When the right leg is reaching the left is pulling. It also has that deliberate movement.

	We are ready to examine the second set of legs and see how their motion fits in with the first set. Lucky for us it looks as though they mirror the front legs. The second leg on the same side is offset by half a cycle like the opposite side. When the front right is reaching, the second right is pulling. This is the exact opposite on the left side.

Let me take this time to point out an observation about my spider. It looks as though his legs are "grouped". The first and
second sets of legs (discussed above) appear to point in a forward direction while his back legs point, well, backward.
Lets look at the back legs now. On my little guy the hind legs are slightly shorter than the front. They do appear to be
pointed backward but the reason is now obvious. It uses its back legs to "push" itself. As the front legs reach and pull, the
hind legs are pushing and retracting. Lets compare the first and the forth legs on the left side.

By looking at one leg at a time the spider walk is not that difficult to understand. The biggest difference from other critters,
that I noticed, is that the front and back legs are divided into two different groups, the "pullers" and the "pushers".
Besides the leg motions and placements mentioned above I also noticed three other important motions. As the spider walks
it pauses ever so slightly between each half cycle. The spider also has a little waddle. His abdomen seems to shift from side
to side when as he places his weight from right to left. His upper body (or carapace) also rises and falls as he shifts his
weight.
This exercise was meant to give you a taste of how you might go about studying a characters motion and looking for the
details that will make your animation more believable. I obviously like to draw out my motions. I think it is a good habit to
get into. We will continue our study while we begin to place keys in MAX.

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