Animation without Inverse Kinematics

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2 comments, last by vrihai 21 years, 2 months ago
Alright. What I want to do is just move my character''s hand to a doorknob or lever, or just any EXACT position. (Like they do in Project Eden) I can find out the final world space position of the joint, but Since I use only rotation keys for animations, I can''t figure how to do this. I don''t want to dive into something so complex and expensive as IK.
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quote:
Alright. What I want to do is just move my character''s hand to a doorknob or lever, or just any EXACT position.


That _is_ IK., there''s no avoiding it.

quote:
I don''t want to dive into something so complex and expensive as IK.


IK isn''t that expensive, especially since you''re only using 2 bones (upper arm and forearm). Googleing will give you plenty of info.
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Depending on the number of joints and their configuration, it is probably easy to find a closed form solution for your IK. That''s not too complex. Just write the equations linking the position to the joint parameters (x,y,z=f(q1,q2,...) ) and try to express it q1, q2,...=g(x,y,z).
If you have more than 3 joints or if some joints are in the same plane, you might have a redundant system or a system where you have to handle orientation too. Then you still can use the "Jacobian" (to linearize the equations around the current configuration) and maybe use something like "pseudo inverse", "Damped least square" or "Jacobian transpose". Have a look with google about that.

A bunch of IK resources here.

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