L6 expressions don't follow IK?

L6 expressions don't follow IK?

Post by Mark Nutt » Fri, 30 Jun 2000 04:00:00



I've got a Bicep bone and a Forearm bone.  I also have a BicepBulge bone
perpendicular to the Bicep bone.  Using an expression for the length of the
BicepBulge bone as follows:

abs(Forearm.rot(Time).p / 10)

Not necessarly the exact equation I want, but enough to observe the effects
of expressions.

Anyway, assuming I have a full IK chain from shoulder to hand, and IK goals
for the hand and elbow, I would think that the length of BicepBulge would
change as I move my nulls to bend my arm, but that doesn't happen.  If I
keyframe the movement of my arms instead of using IK, then the length
changes more or less as I would expect.  Also, I can workaround by creating
keyframes for the Forearm bone everywhere there's a key for the IK goals --
if I move my goals, the keys all auto-update, and the bone length behaves.

Still, I'm surprised that with pure IK (without duplicating keyframes for
the Forearm bone), expressions don't seem to "see" the bones moving at all.  
Is that the way they're supposed to work?

Mark Nutter

Yesterday is tomorrow.

 
 
 

L6 expressions don't follow IK?

Post by Arni » Fri, 30 Jun 2000 04:00:00



> Still, I'm surprised that with pure IK (without duplicating keyframes for
> the Forearm bone), expressions don't seem to "see" the bones moving at all.
> Is that the way they're supposed to work?

Channel modifiers are evaluated prior to IK solving (as they have to
be). Use the IKCapture motion plugin to automatically keep the keyframes
in sync with the IK derived motion.

 
 
 

1. Expressions follow expressions

Hi,

does anyone know how to make an object follow another object that is
parented to an object that is driven by expressions ?

In other words, I have an object that is driven by expressions, and a
null is parented to it. How can I have a third object follow the child ?

Another expression, Follower, and Relativity all do not work.

thanks,

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