I have a demonicish character, and he has an extra “knee” I have tried to get him to set up in motionbuilder but i am missing some key part here, since it always attaches the IK from the first knee straight to the foot, leaving the second knee unbending.  Is there a way to aadjust the character for all the knees to be included in the system?

I’ve included an image of the leg as an attachment

	Attachment

treat the second “knee” as it really is, the ankle and you should be ok.

you could also dirve a regular leg with the rig and use constraints to map the data to the creature leg.

also look in to the quadraped rigging examples.

Brad Clark
Co-Founder: Rigging Dojo-Teaching the art and science of character rigging
Author: Inspired 3D Advanced Rigging
The Character Animator Toolkit for Motionbuilder :available now:

i’m not sure what you mean in the first part.  Can i assign the “ankle” so that motionbuilder understands it’s movement?  I tried just using the foot and toe joints as the extra joint and foot, but that was wrong as well?

hip-knee, second knee, your skel ankel.. would map to be… hip, knee, foot , toe in the character, you will want to straighten it out though before you characterize.. again look at the docs for the quadruped example, even if you don’t use the quadruped rig.

if you don’t straighten out the leg then it will set some strange limits on the rig and not work how you want I think. 

after you will have to adjust the character ankle height setting to help with the solve as you might want to reparent /adjust some foot control rig ctrls to make it easier to work with.

Brad Clark
Co-Founder: Rigging Dojo-Teaching the art and science of character rigging
Author: Inspired 3D Advanced Rigging
The Character Animator Toolkit for Motionbuilder :available now:

hmm the only quad example i could find was the cat running, and its leg rig is horrible.  With the current setup, i would have to rotate the second knee like it was the foot, then also the actual foot since its the toe, this is very poor for a configuration, I think i will go for having a leg setup with just three joints in MB and translating that into a control rig in maya.  it would be nice if i could just control the IK handle generation myself, i dont guess this is possible?

You would be able to move the pivots of the foot CTRL, to rotate from the correct location or create a new foot rig while leaving it characterized that way. 
The other option is to characterize the lower part of the leg and create a custom upper knee rig, again the need for something custom would be required.

You can use the IK constraint for that..  and maya would read it in as an IK.

A real animal leg is just a human leg up on its toes.. I would just make the foot rig work the way I want… we had a horse rig setup with the quad rig and a custom shoulder FK rig.

I cover custom foot rig creation in the DVD if you need a full how-to.

I do wish it was a bit easier to have control over the character definition but its not to bad to work around with all the options of pivot, aux and handles.

Brad Clark
Co-Founder: Rigging Dojo-Teaching the art and science of character rigging
Author: Inspired 3D Advanced Rigging
The Character Animator Toolkit for Motionbuilder :available now: