View Full Version : Follower Modifier, and targetting a null.

05-27-2011, 02:35 AM
Hello, I have a problem with animating an object. My rigsetup is

Thumb Bone
-Following Null movement X Z Y (World cordinates)
-Target Null (Left)

The issue :

On my left side I have the exact same setup, and the handel follows the hand nicely, and I can rotate the bank axis to get it to align nicely after the rotation of the arm.

However, on the right side, once I target the handel to the null on the right so that it always contsrain it's aim towards it, it snaps. It's aim is totally off, and if I rotate the bank axis, it snaps back into the correct place, and it aims perfectly at the null. However as soon as I start running the animation, it snaps back into bogus land.

Here are some pictures to illustrate. Red area marks shows that they both function as long as they are aiming at the left Null, however as soon as I target the null on the right, with the right handel, you can see how it has snapped out of place and isn't aiming at it at all.

The left handle had the same problem, however it obeys the Bank rotation, and doesn't snap back into place, unlike the right side.

Bug? :screwy:

http://img231.imageshack.us/img231/7340/68262397.jpg (http://imageshack.us/photo/my-images/231/68262397.jpg/)

05-27-2011, 02:46 AM
I fixed it by just re-rigging it, adding a new null parenting it under the thumb , and then making a new copy of the handle etc etc.

This seems like pure luck to me, I would like to know exactly why this error occured if possible. Cheers.

05-27-2011, 03:21 AM
Its an evaluation order issue.

Target is a motion controller, and as such is evaluated alongside IK (happens at the same time) which, normally, is after motion modifiers (which is what follower is).

Now by setting follower to after IK, it should evaluate second, the target evaluating first. This itself may well cause the issue, but sometimes it can be a trick to get things to evaluate properly anyways like this, parent space, and other lil things can get in the way and confuse the whole situation.

Making the copy, and reparenting as you've done let's you jump the "gap" as it it were... but the better option for doing something like this is to not use follower, but instead use the same as item control which is evaluated alongside IK target, and the rest of the things on that same panel, and which will work properly and transparently alongside them.