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aforetaste
01-27-2006, 02:21 PM
Okay, I realize that this should be Messiah 101, but...

When I create a simple IK chain with a target null, I can never seem to figure how how to parent the null to the chain so that it will STICK to the last bone.

When I move my null around (moving the chain) it wanders all over the place... often way out in space. Can you pin the null to the last bone?

I searched the docs but no luck.

thanks in advance.

SpikeWorx
01-27-2006, 02:30 PM
Donīt use parenting to lock the goal(target) to the end effector.
Make the goal independent of the IK Chain hierachy and use the LockedGoal expression to constrain the goal to the end effector: LockedGoal(EndEffector, Goal,1)

aforetaste
01-27-2006, 03:07 PM
Thanks SpikeWork,

My expression reads:
LockedGoal(Null,Skeleton_Bone_5,1.000000)

But that doesn't seem to be doing it. Now the Null is simply locked into place (it would seem). I can't move it anywhere.

Also, it says in the description of the LockedGoal:
The second object variable (goal), will move to the position of the first (endeff),...

Doesn't that mean that the expression should read:
LockedGoad(Skeleton_bone_5,Null,1) ?

SpikeWorx
01-27-2006, 06:21 PM
Thanks SpikeWork,

Doesn't that mean that the expression should read:
LockedGoad(Skeleton_bone_5,Null,1) ?
Indeed. I think in your case the endeffector of the Ik chain is your last bone.
Itīs also important that the expression is calculated after IK.

aforetaste
01-27-2006, 07:13 PM
Sweet!
That did it.

Now, how do you know when an expression should set to operate before IK or after?
Trial and error?

Isn't there a logic to it all?

SpikeWorx
01-27-2006, 08:25 PM
Sweet!
That did it.

Now, how do you know when an expression should set to operate before IK or after?
Trial and error?

Isn't there a logic to it all?
Yes, it is :)
After IK means the expression takes place after the ik solve. Thatīs what you want in this case ;)
Some expressions require the state after an ik solve. Others the state before the solve happens. Simple logic and the expression system of messiah allows for flexibility. I love it.
Just think of it as a kind of batch processing. The order of the expressions determines the order of execution. Simple steps, one after another.
If you know what each expression does, itīs very easy to see the logic behind it .

JoeCosman
01-27-2006, 08:32 PM
beforeIK= when you just want it to execute in order down the list

AfterIK= when you want to jump order(usually after you set an IK goal in the animate tab)

motion= apply during moving objects that are controlled by expressions and effects.

aforetaste
01-28-2006, 01:26 AM
Thanks guys.
That gives me a good start on grasping all those wires under the Messiah hood.

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