Joint pivot shift

Issues concerning rigging & Face Robot...
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Pancho
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Joined: 19 Sep 2010, 11:28

Joint pivot shift

Post by Pancho » 08 Mar 2013, 16:25

I wonder how this could easily done with a rig made in Gear. In a pure Ice rig I'd find a way, but the ice rigs so far were very slow and no fun to work with. Therefore I would like to use gear as a base for all Si rigs.

But how could i cange the pivot of the ongoing rotation of a joint like the knee joint? For those not familiar with the problem: While the lower arm rather rotates around a well defined axis, the knee doesn't. Its joint rather works like a cylinder rolling on a plane. This way the "virtual" axis of the knee moves depending on its rotation angle.

The only way I could think of right now is to add another bone as the knee and change this bones length depending of the angles of the ik chain to simulate the real joints behaviour.

Cheers
Pancho

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rray
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Re: Joint pivot shift

Post by rray » 18 Mar 2013, 11:40

Just an idea, could a joint that's placed higher work for this? (around 10 cm above the "actual" joint)
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mattmos
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Re: Joint pivot shift

Post by mattmos » 18 Mar 2013, 11:56

That might be the best option, although you would probably be best off having a second enveloping limb, use the traditional 2 bone leg and have a second chain with the knee bone which follows the first, that way you can still Fk/IK switch easily and the 3rd bone only affects the positioning of the envelope objects.

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