Parent constrain Geo offset weirdness

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  07 July 2005
Red face Parent constrain Geo offset weirdness

If this make sense, I have a stretchy spline Ik solver on a tail, and the stretch is along the x axis, done with a curveinfo node archlength feeding into a multiplydivides node, operation set to divide, then the output x fed into the joint scalex, it all seems to work nicely, but now when i parent constrain the geo to the joints, rotate the controls, everythings fine, but when i translate them, esentially scaling the joints, the geo flips out all over the place, anybody know why this might be happening?
  07 July 2005
I donīt know exactly what you mean by "freaking out" but when I set-up a stretchy chain I always use the translate attribute of the joints to make them stretchy. Scaling sometimes gives weired results. Maybe you get shearing on your geo if you are not directly parenting it to the joints, but I dunno.
for using the translation on the local-aim-axis of the joint you would need some more multiplyDivide nodes to set the chain up because every joint will have a different (in your case) translate X value. might take some more time to rig, but for me it always works like a breeze.
hope that helps.
  07 July 2005
Originally Posted by craigs: ... joints, the geo flips out all over the place, anybody know why this might be happening?

Check your rotations on your joints first (display the local rotation axis on them). It looks like the spline ik is wreaking havoc on your rotations possibly because you haven't set up your joint orients correctly.

This might also happen because you have chosen a rotation order that is not working well for how your joints rotate (causing extreme rotational jumps)

Also, if you want to go down the constraint route to hold your geo to the joints you need to make sure the rotation order matches between geo and joints

If nothing works get rid of the spline ik and look what happens if you just move the joints around manually. this will tell you if the spline ik scews things up or if the constraints are the problem (or shearing on the geo as cavetroll suggested)

Matthias Zeller
3D Artist / TD
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  07 July 2005
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