View Full Version : stretchy leg setup!

08-15-2006, 11:25 PM
Hi guys !

im trying to create a really simple character, made of simple geomatry so i can have aplay animating it.. so heres a picture of the leg structure:
hope you can see that basically a bunch of spheres and cylinders. simple enough yeah ..

so i set up you basic IK leg with a reverse foot,I added some stretch to the IK, however i got the spheres stretching more than the inbetween parts, which frankly looks wrong.

so i have tried using another joint between the hip and knee and onebetween knee and ankle... so i can stetch the middle joints instead of the hip,knee and ankle ... ( the thigh and shin section will parent onto the middle bones.

though now i am having problems keepign the geomatry from 'breaking' apart
geomatry (http://www.gimbal-lock.net/geomatry.avi) bones (http://www.gimbal-lock.net/joints.avi)

is there some kind of constraint i can use to fix this.... in fact was using extra bones the best way to fix this ?

any help would be appreciated


08-16-2006, 03:52 PM
An alternative would be to rig with Anzovin? Studios TSM2(setup machine).
Its a great rig and theres a plug on highend for better hands.

08-16-2006, 08:50 PM
Can youjust constraint the sphere to the leg instead of skinning it (the knee sphere for example)? IT sounds like the skin/cluster or whatever you are using is getting the scale as well (which makes sense). That way you would have the legs parts stretching and the sphere would stay "sphereish".
Maybe not what you are trying to achieve?

08-17-2006, 08:24 PM
hey guys,
thanks for the advice!

hi animation rigs, i have used constraints to get the geomatry bound as you suggested, and used the stretch method from alias supertoons DVD.

works really well :). I added a group based reverse footsetup also. It pretty much is all good. But when i stretch my leg, the toe bone flips up as if it is bieng left behind. I tried to just counter aniamte it and the reverse foot setup isnt letting me move it enough.
any ideas what might be up?


08-18-2006, 01:59 AM
I would be happy to try helping, as I would then know better for myself... but I dont know the supertoons method. Could you share what you have done? Then we can all fix, and have another good leg rig.


was playin with a robot leg and... for me, I simply gave each part there own joints, skinned and wieghted, smooth(rectangles) or rigid(spheres) as needed. I received nice stretchy legs, and the spheres dont distort.

08-20-2006, 02:57 PM
Hi Rasamaya,
sorry took me a while to reply!

Basically the setup uses a null group snapped to the hip(null1), freeze the transformations, duplicate it (null2). Parent null2 under null1. Snap a locator onto the ankle joint.

aim constrain the null1 to the locator and point constrain null2 to the locator. (so that it jumps over to the ankle). ok so in the hypergraph, created a multiply divide node plug null2's translate into the input 1 and enter the same figure into input2. (set the node to divide).
create a condition node(to make it stretch only when past full reach).

plug the outputX from the multiply divide node into the first term of the condition node. Change the second term to 1.00 and set to greater than.

Also plug the outputX into the coloriftrueR of the condition node.

Right nearly there. I created one more condition node (this one is to see if the custom attribute on the footcontroller has the stretch mode turned on).

plug the outcolor from the previous condition node into the coloriftrueR of the new condition node.

And the attribute for stretchyness from my foot controller (.stretchy in my scene) into the first term.
change the secodn term to 1.00 and set to equal.

lastly i took the outcolorR from the condition node and plugged it into the scaleX of the bones i wanted affected.

I think this is pretty much the same as the other ways of doing stretchy joint stuff.
heres (http://www.gimbal-lock.net/mrballlegsetup.mb) my scene file if your interested (maya 7.0)

still not sure whats going on with the toes tho :/

i might try the joint for each section and rigid bindd the spheres... as i have them deforming at the moment and it is a bit of a compromise


08-21-2006, 05:18 AM
OK....how about trying out a couple of things:

a) Lose the joints you have put in the middle of the thigh>knee and knee>ankle chains
b) Snap the pivots of your geometries to the corresponding joint which will move them, i.e., the pivot of the sphere and the cylinder under the sphere which will be deformed by the knee joint should be on the knee joint...
c) Don't skin. Parent Constraint your geometries to the respective joints. Like I said above, parent contraint the sphere and the cylinder under the sphere which will be deformed by the knee joint to the knee joint.
d) Now simply feed in whatever values ou are calculating directly into the scale parameters of the cylinders, scaling spheres doesn't make much sense

Hope this helps. :D

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