All Things Digitigrade Legs

A preface for the uninitiated: A digitigrade is an animal that walks on the toes of its feet, rather than on the whole feet. Real examples include things like cats, dogs, cows and ostriches, while fantastic examples include things like werewolves, minotaurs, were-cats and, um... Chocobos... When I say "digitigrade legs," I'm talking about the hind legs or quadrupeds, as they are what's classically seen as the so-called "backwards knee legs."

The reason I'm making this thread is because I want to see if you guys can help me paint a clearer picture of what a bipedal humanoid with digitigrade legs would look like. There have been many designs over the years, and I myself have posted pictures and screenshots of many of them. The digitigrade legs we have (the Moster legs) are... Really not something I'd consider to look natural, or indeed look good, but if not that, then what? That's the primary question I'm looking to answer here.

I don't want to look to nature for rules already stated for a couple of reasons. First of all, the few bipedal digitigrades that exist are almost all birds and as such have bodies that are pretty far from looking humanoid and, even then, their leg bones are too dissimilar from human to really apply. Secondly, while digitigrade stilts do very much exist for actual humans to wear, there are multiple problems with these. For one, we're build to walk upright with our knees locked, so we instinctively try to walk as close to that as we can in these stilts.

For another, human muscles are built for a relatively short foot, so digitigrade stilts tend to cheat, either by extending the walking surface back from the toes, by shortening the stilt by moving the shoe position down or by using bungee cords to hold the stilt extended. And even when humans do walk in these stilts, the problem is that they lengthen the overall leg size significantly beyond what looks humanoid, making them look like they're 10 feet tall with 8 feet of legs.

Personally, I'd like to concentrate on fictional designs, such as the legs we already have, the legs on the various Fantasy demons (such as those on the Heroes of Might and Magic 5 Succubus), or even those on giant robots (like Metal Gear Rex). So, with that in mind, what do you believe digitigrade legs should look like? How do you believe a person with them should stand? What would be the correlation of lengths between the thigh, shin and foot?

Counting the hip joint, the human leg has four joints - hip, knee, ankle, toes (counted as one joint). As City of Heroes handles it, the hip joint and thigh size are very much identical to those of ordinary legs, with the "digitigrade" part of the Monster legs consisting of an extension replacing the lower part of the leg. I'd call it a boot extension, but boots only extend below the knee, whereas these legs actually extend from the knee itself, which is held bent backwards at all times. This looks really awkward to me both because it's not a natural stance for someone with legs like these, and because it actually cuts down on the length of the shin in comparison to the thigh. Even in the few bipedal digitigrades (say, the ostrich), it is the thigh which is incredibly short and stocky, with most of the leg being shin and foot. The "backwards knees" themselves are actually ankles, not knees at all.

Personally, I would assume a creature like this would stand with its feet held much more vertically, putting less stress on the ankle joint in holding the body up, as well as less stress on the toes. I'd also expect to see the knee held up much farther forward, with hip joint actually bent forward. I'd also expect the thigh to be much shorter, at most comparable to the length of the shin and the foot. Being that I suck at artwork, I can't really draw what I mean, but I'd say the Succubus I linked to before has the right idea.

Now, I understand why the digitigrade legs we have here in City of Heroes are done as they are. With only the lower legs being basically a boot swap, the digitigrade legs can use the same animations as the more proper legs. And I will admit that it's true - I can't actually think of a single other game which features a digitigrade protagonist with this kind of depth and breadth of animation diversity. What City of Heroes does is the equivalent to the the Prince of Persia if the Prince were a Satyr.

This is kind of where this whole thread came about. Since it's foolish to suggest adding a brand new lower legs skeleton to be animated completely over again, I got to thinking if it isn't possible to come up with a mathematical model for transforming regular-leg positions into digitigrade leg positions completely automatically. But then it occurred to me that I don't really know what the corresponding positions to real-leg stances would be, which brings us back to the question: What do you believe a bipedal humanoid digitigrade would look like?

Quote:

Originally Posted by Arcanaville Samuel_Tow is the only poster that makes me want to punch him in the head more often when I'm agreeing with him than when I'm disagreeing with him.

You need to add a [/url] to the end of each of your links.

Done.

Quote:

Originally Posted by Arcanaville Samuel_Tow is the only poster that makes me want to punch him in the head more often when I'm agreeing with him than when I'm disagreeing with him.

ok, norton sent me 4 warnings for those links. just saying.

Take the Magic: The Gathering 'What Color Are You?' Quiz.

That mecha looks more like it was based on a dog's hindquarters than trying to make humanoid digitigrade legs. The succubus is better.

As for a transformation from normal to digitigrade legs, the only thing I could think of that looks halfway decent would be something along these lines:

1. Have an animator move the digitigrade legs to something at least close to what they want for each keyframe in an animation. (That's assuming these are keyframed animations, which I'm not sure of. It also needs to be done manually.)
2. Create a transform between the normal leg's keyframe and the digitigrade keyframe. (This is actually fairly simple: simply map 3 points on the regular leg to 3 points on the digitigrade leg, and press your magical 'calculate' button. I would recommend knee, ankle, toe as the points.)
3. Repeat steps 1 and 2 for all keyframes in the animation. Manual modifications to the transform or new keyframes may be needed if a digitigrade animation does something bizarre like flip a foot upwards throgh the shin.
4. Repeat steps 1-3 for every animation.

Okay, I officially love this thread. Digitrade legs are really cool and I love the idea of them.. and this is tons of both information and things to ponder on!

I know the aliens in The Arrival (with Charlie Sheen) had legs with reverted knees and I believe they ran on their toes. The didn't know a ton of them moving around like that, but the locomotion looked a lot like an ostrich to me.

Are Zentradi Mechs Digitigrade? I allows thought those wear the coolest. Palladium let you play as an earth aligned Zentradi officer in one of the later Robotech RPGs and they had similar mechs but they had arm cannons with these wee little hands.

Found a pic here

I don't think it would be possible to have the thigh and calf be a replacement for the thigh, and the foot be a replacement for the calf. The problem is that the ankle is then doing the full duty of the knee, and it simply doesn't have the range of motion to make that look good. Imagine what happens if such a rig were to kneel: the ankle would hyperextend backwards until the foot was resting against the buttocks. That would be bad.

Incidentally, the current rig looks poor when standing straight, but as soon as you get into the combat-ready stance with the knees slightly bent, it looks a lot better. It could just be a matter of getting the character to carry itself appropriately. If the idle stances were adjusted for digitigrade legs, that might get us most of the way there.

Also, I want that succubus's legs, but more than that, I want her gloves. An option for large organic hands in addition to the large robotic hands we have now would be wonderful. But that's for another thread.

Something like kneeling would be done differently, where they wouldn't been on their knees at all but resting back on their heels and possibly leaning forward down between their knees.

How about anyone in high heels?