Biped Woes

Mastasurf

I'm working on my 3d final right now. I have an Emu that is rigged up with a biped. Being a jackass an all I overlooked the fact that Emu legs bend the opposite of humans. Does anyone know of a quick and dirty way to get the calves to bend forward instead of back? I tried rotating the leg around 180 and it twists the mesh even in figure mode. Please help!

Joshua Stubbles

Nice to see ya here, Masta.
I veer away from Biped altogether, though. I usually make an IK bone rig. You can also try stuff like CAT

NoSeRider

My guess would be is change the direction of the IK in the legs.........

But I'm with Vassago, I hate Character Studio....with a passion.

Eric Chadwick

Biped has its benefits though, can be good for beginners, Bips are easy to save and re-use.

Anyhow, emus are probably like ostriches and cats, their thighs are very short, and they walk up on their toes. If you want to use Biped (or need to because it's a class), just lengthen the toe bone, raise up the foot bone to be the "ankle," etc.

FatAssasin

There's an option in the biped setup section to change the number of links in the leg from 3 to 4, for exactly this reason. But personally, I don't like the way the leg behaves when you try and move the foot around using the extra link, so I do what Eric said, which is to make the toe extra long. It's also more anatomically correct to use the same number of bones as a human leg.

The legs on animals don't bend backward, they bend the same way human legs do. Check out this page on animal anatomy to see how human's and animal's legs compare.

Basic Anatomy of Mammals

Mastasurf

Hey Vass, Thanks for the tip on rigging tools. Saddly i'm not going to have time to put in another skeleton :-(. This is due Wed and I need time to render.

noSeRider: Do you know where and how I would do that? Right that would be the ideal thing to do. If you do that would be very helpful.

and..



They do bend the opposite direction as humans

FatAssasin

You can't change the direction of IK on Biped legs, or on regular bones as far as I know. If you don't have time to put in a new skeleton then sorry to say, you'll have to work with what you have.

And technically speaking, the legs don't bend in the opposite direction as humans. The link I posted shows what's going on. If you're really serious about modeling and rigging creatures you need to study anatomy, not just look at pictures of live animals.

What you think is the knee would be the heel on a person, and the part of the leg that's parralel to the ground in that picture is equal to our foot. What is the knee on a person is higher up on the Emu. You can see the slight bend where it's covered by feathers, and you can see that it's bending the same way as a human leg.

monster

I agree with FatAssasin. Birds are not mammals, but their legs have close to the same anatomy.

If you need a quick fix you can add a sub anim contoller to the biped, say a EulerXYZ. Then enable sub anims and this will allow you to rotate the knee 360 degree in any direction.

OR

Bake the skin weighting to a mesh using the Skin Utitlies found in the Utility Panel. Remove the skin modifier, fix the bones, and reapply the baked mesh. If you used physique, use the Physique2Skin tool at sparks.discreet.com

Joshua Stubbles

Listen to Monster, Masta. He's the man
We actually have him skinning our characters for rigging right now.

Mastasurf

Oh! Thanks monster, i'll give that a try later tonight :0). I wasn't aruguing about the anatomy of the legs was completely different. I was just trying to say that the biped IK is prohibiting me from rotating the calf forward. Anyways, Thanks again for the quick replies. Hopefully one of monster's fixes will work.

Eric Chadwick

Mastasurf,

You don't have to convert to bones if you don't want to, although bones certainly have their benefits.

Here's a character we did with Biped, it has a similar bone structure to your emu.
http://www.whatif-productions.com/Images/2004.03.17_sengokustreet_0002.jpg
His heel is the backwards-looking joint that may seem like a reversed knee. It's just that he's standing up on his toes.

We merely rotated the Foot bone up, scaling the Biped leg bones appropriately. So you can use Biped for this if you want, although in the long run you'll be better served by using bones.

Here's a skeleton I found.

The thigh is extremely short, the knee being level with its ribcage. So the backwards-looking knee is really the heel.

Mastasurf

Now I see what you guys are saying about the thigh bone. The image of the skeleton really helped. I think if I want to do any serious animating with this character i'll have to remodel it so the legs attach up higher.