CGTalk - Two joint Knees?

JookBoxer

12-08-2009, 06:31 PM

For a leg setup. I have seen seen legs that use two knee joints.

My question is, what advantages does a two joint knee have? Why use two joints instead of one?

Look at the picture for reference. The hierachy goes like this.
HipJoint->Firstknee->SecondKnee->ankle->ball->Toe
The first knee and second knee are almost at the same positoin.

http://i849.photobucket.com/albums/ab56/JookBoxer/TwoKJ.jpg

Lomax

12-08-2009, 10:14 PM

The main advantage that I'm aware of is that it helps maintain volume in the knee.

musi

12-09-2009, 11:20 AM

Yes, it is a deformation issue two joint knees are solving. It helps keeping volume in extreme poses, like say character kneeling and the heel is very close to the hip joint.

wwswimming

12-09-2009, 02:38 PM

Yes, it is a deformation issue two joint knees are solving. It helps keeping volume in extreme poses, like say character kneeling and the heel is very close to the hip joint.

somehow the character with the reverse-knee-joints in the sci-fi movie "The Arrival" comes to mind. that was good sci-fi.

http://www.imdb.com/title/tt0115571/

released in 1996. with Charlie Sheen.

Darksuit

12-09-2009, 02:46 PM

Aside from maintaining volume and shape really well, the Two knee joints does is it prevents the leg from flipping. Due to the nature of IK, with two joint it reduces the ability for the leg to flip with two joints to an almost zero percentile.

giordi

12-09-2009, 04:26 PM

all said above is totally true , if you want to check is really easy create a cube scale it on y axis and duplicate it know draw two bone chains , one with double knee one without do a bhind skin and rotate it on the knee you will see the big difference on it!

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12-09-2009, 04:26 PM

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