View Full Version : Non IK IK legs?

04 April 2006, 06:50 PM
So is there a way to create legs that mimic an IK setup, but without actually using IK? Basically, what I'm after is a foot that can translate in Z, without the joints of the foot popping off the ground when they go past the limit of the leg joints above in the hierarchy. So basically you'd be able to translate the foot in Z off into infinity and it'd stay on the ground, while the leg just stretches.

Also, if anyone has a good tutorial on how to create a non-flipping knee, I'd be interested in taking a look! =)

04 April 2006, 07:55 PM
Yup, this is duscussed in the cgtoolkit art of rigging book - what you pretty much do is measure the length of the upper and lower leg bones and keep the total of the two. Then you use a utility node to check the distance between the ik solver and the top of the upper leg bone. If the distance of the ik solver goes further than the length of the upper and lower leg bone combined you use a multiply / divide to work out the current length of the distance between the hip and ik solver divided by the length of the two bones lengths.

Lets say the upper bone was 5 units length and the bottom leg was also 5 units length so 10 units in total. Now lets say that the ik solver has moved 15 units away from the top of the upper leg bone, what we do is divide the new length of 15 by the original length of the two bones or 10, this will give us 1.5 - We can now pipe this 1.5 value into the scale of the upper and lower leg bones along their length so that the legs will stretch to make up the distance between the hip and the ik solver. To retain the volume of the legs you have to do the inverse and remove a certain amount of scale from the other two scale values of the bones on their respective thickness so that it looks stretchy.

Sorry I can't give you specifics since I'm a max op but that's the way the cg toolkit book does it.

05 May 2006, 12:11 AM
I had posted a non flipping leg (maya file) in this other thread if your interested.


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05 May 2006, 12:11 AM
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