Gait Analysis

Does anybody know of any good sites that go into detailed explanations of different gaits? Different meaning two, four, six, and eight legged.

That type of resource is hard to find. What do you want to know? I’ve studied most 2 legged and 4 legged gaits in great detail. I’ve even looked at 3 legged because I had an amputee cat!

Obviously with 2 legs you can either step or hop, at various extremes of stride length (either with a jump or without). That gives you walking and running, or variations on hopping and skipping.

With four legs there are variations on walking. Animals with stiff backs, like horses, generally move their legs 90 degrees out of phase, so that the front legs are “passing” while the back legs are at their furthest separation. This gives them a regular “clip,clop,clip,clop,clip,clop” pattern when you hear them walking. However, if you look at flexible animals like lions, you find that they lope along in a less regular motion. There is only a slight delay between the movement of the hind leg and the one directly in front of it. The lion’s body sways side to side as it walks. And then, some dogs (particularly older, arthritic ones) walk with the two legs on one side of the body moving in unison. It’s like two people marching along, one behind the other!

Once you introduce a hop into the gait, you can get trotting and pacing (in horse terms). There is also racking, which applies to camels, and there are words for the equivalent dog movements. Anyway, in trotting the diagonally opposite pairs of hooves strike the ground at the same time. In pacing, the hooves on one side strike the ground together, and then the other. Pacing is more energetic, but smoother and faster.

Then you can have cantering (I’m not sure what animals do this other than horses). That is a three-beat gait, where you have one hind leg striking the ground, then the other hind leg and diagonally opposite fore leg striking together, and then the remaining fore leg. Horses can do a “flying change” while cantering where they change which fore leg leads the canter, and if they do flying changes at every step they can go into a funky “skipping” kind of gait :slight_smile:

Then there’s the gallop, which is a four-beat gait. One hind leg, then the other hind leg, then the diagonally opposite fore leg, then the remaining foreleg strike the ground. There is a point at which no hooves are touching the ground during a gallop (as Eaweard Muybridge discovered over 100 years ago).

Cats have their own method of running where they leap forward with their hind legs and land on their forelegs, then repeat. This takes a lot of flexibility in the back. Sometimes their paws don’t strike the ground at the same time, sometimes they do. I haven’t studied this enough.

So, how do six-legged creatures move? I’ve only ever seen them walking, and have never seen a walk that didn’t involve diagonally opposite pairs of legs moving together. I think some bugs move three legs at once and then the other three, and others move them in a pattern of three pairs (one after another). I haven’t studied that much, but I think the second type of movement is more convincing.

Spiders always seem to have legs going everywhere, so I think they move them in diagonally opposite pairs. Perhaps two pairs at a time?

I’d be interested to hear from anyone who has studied bugs and spiders!

Oh, I forgot lizards! I get the sense that they pretty much move one leg at a time in a slow walk. But they always do things in such a way that their back has to bend into an S shape, so they really stress those diagonally opposite pairs.

Also, big animals like elephants go close to only moving one leg at a time as well. They can’t easily support their weight on two legs.

Oh yeah, I still have some old animations online that illustrate some gaits:

Horse (all Bink executable files, so they run on any windows computer without codecs needing to be installed):

Walk - http://lisa3d.org/cadsagap/walk2.exe

Trot - http://lisa3d.org/cadsagap/trot.exe

Canter - http://lisa3d.org/cadsagap/canter2.exe

Gallop - http://lisa3d.org/cadsagap/gallop2.exe

(Rearing on hind legs - http://lisa3d.org/cadsagap/rear.exe)

A marsupial lion walking (Thylacoleo Carnifex) - http://lisa3d.org/animations/MainWalk%20Sor3%2002.mov

That’s a Sorenson 3 Quicktime. A paleontologist apparently said my animation was very authentic!

Well, something that desribes each phase of the walk cycle of a biped in detail with many graphics and animations along the way. (i.e. hip rotations, spinal compression, etc.) Basic human kinematics for both male and female at the very least. 4, 6, and 8 legged walk cycle analyses would be much appreciated bonuses, but I’ll understand if basic descriptions are all that can be found. Anyway, I’ll go searching again right now…

I once wrote code to control the gait on a hexapod (six-legged) robot. There are two primary means for 6-legged creatures. One is the alternating tripod gate (front and rear of one side, along with the center of the opposite side… one set lift and moves foward while the other set pushes back to give forward locomotion). That one is the most common. The other one is more common in heavier hexapods. With this gait, only one leg is up at a time, going from rear to front (rear right lifts and moves forward while the other 5 push back 1/6th of a full rotation, the the rear left lifts and moves forward while the other five move back another 1-6th).

There are one or two other, more esoteric ones, but those are the most common. Not sure so much about 8-legged creatures, but I’m fairly certain it can be derrived from one of the above. For research, you might want to check out some university robotics research labs. They usually have a lot of data on various gaits. IIRC, the MIT robotics lab had a really good resource.

Hope that helps.

EDITed to note that the second gait that lisae pointed out was also fairly common.

Thanks for the info !

There is some info on horse gaits on Wikipedia.

Have you seen the horse rig here ? http://blenderartists.org/forum/showthread.php?t=72096

There are video references in that thread too.

Mike

Hmm, found a site with a good word description, but graphics would still be helpful… It also neglects to point out the difference between male and female gaits.

link

[Edit] Found another helpful site, but still no graphics. link

[Edit 2] Found one with graphics… link

The main difference between a “masculine” walk and a “feminine” walk (both males and females can have either of these), is in terms of how far apart your feet are through the walk cycle. For a masculine walk, the feet stay quite separated through the walk. For a feminine walk, you put one foot in front of the other.

This means that when you see the walk from the front, the masculine walk doesn’t have much hip sway at all, and there is visible space between the legs. The feminine walk has a lot of hip sway because she has to kind of move around her legs! And there is no visible space between the legs. Having the feet one in front of the other also gives her more of an hourglass appearance, because the legs taper down to the feet.

From the side view, a masculine walk might involve puffing the chest out (moving it forward) so the man looks strong. A feminine walk might involve moving the hips forward.

One tip - if you want to study female walks, don’t look at cat walk models! They have a really jaunty walk that’s designed to make their clothes swish around and their boobs jiggle, because they’re trying to show off a particular kind of fabric or the cut of a dress. It’s not very realistic :stuck_out_tongue:

Some great info from Preston Blair’s book(s):

http://www.animationarchive.org/pics/pbanimation26-big.jpg
http://www.animationarchive.org/pics/pbanimation27-big.jpg
http://www.animationarchive.org/pics/pbanimation28-big.jpg
http://www.animationarchive.org/pics/pbanimation29-big.jpg
http://www.animationarchive.org/pics/pbanimation32-big.jpg

Mike

Wow, Mike S, those are great! Thank you!