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View Full Version : IK arm with pole vector: elbow won't bend



Spinland
01-25-2013, 07:22 AM
I set this up in accordance with Lino's NewTek tutorial video, and have gone over it several times and can't find any problems. Yet, no matter where I move the goal object the elbow refuses to bend. It seems like the pole bone being targeted at the goal keeps the upper arm always pointed at the goal (I've experimented with untargeting it and the elbow then bends but I lose some control) so the elbow never has an opportunity to bend, but I can't turn up anything differently I should be doing. I've checked to make sure IK is enabled. Can anyone help?

Attached is a copy of the LW 11 scene file.

Many thanks in advance!

Spinland
01-25-2013, 07:58 AM
Okay, I think I might have found a problem. If I alter that rig I attached so the rest positions of the upper arm and forearm are not in line with each other, but bent to some degree, the elbow starts working properly. So you can't use IK chains on straight limbs, I take it?

RebelHill
01-25-2013, 08:25 AM
No, always gotta have prebend, else the IK doesnt know which way to bend.
Check this... http://www.3dworldmag.com/2012/12/20/tutorial-get-to-grips-with-lightwave-ik/

Spinland
01-25-2013, 08:36 AM
Cool, thanks!

This is turning out to be quite the useful learning project. :-)