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Rigging troubleshooting: detaching controls

PostPosted: Thu Mar 15, 2012 5:55 pm
by BenChang
Question: Help! my controls detach from my rig when I start keying things!

There are probably a lot of reasons why this could happen, but here's one common culprit: when using constraints, make sure you don't set any keys on the constrained channels

Here's a way to demonstrate the problem.

1. create a cube. name it "Box"
2. create a NURBS circle. name it "BoxControl".
3. point constrain Box to BoxControl (remember, select the controlling object first).
4. moving BoxControl should move Box as well.
5. select Box and set a key.
6. now try moving BoxControl. Box doesn't move with it!

If you look in the Hypergraph, you'll discover a new node has been inserted between the Point Constraint and the Box, called "pairBlend1". This blends between the constrained value and the keyed value, and defaults to 0 so the output is the value from the keyframe on Box.

To change it, select Box, and look for the new attribute called "Blend Point 1". Change it to '1' and the point constraint takes over.

in some cases PairBlend can be very useful, but here it's just getting in the way.

What you really want to do is not set keys on Box in the first place - keep it on a templated layer so you don't accidentally select it and key it.

The same goes for joints and IK - you can keep those on a hidden layer and then you don't have to worry about accidentally setting keys on them.

Another way to reduce the chance of running into this problem is to use regular parenting instead of parent constraints when possible when setting up the hierarchy of control curves.

Locking channels

It's also a good idea to lock and hide channels that you don't intend to set keys on. To do this, open the Channel Box, select the channel, go to the little Channels menu, and choose "Lock Selected" or "Lock and hide selected." This will make it so you can't key the channel. However, itcan still be controlled from other node connections. On IK and joints, things you shouldn't really be selecting during animation anyway, you can just use Lock. On rig controls, you can Lock and Hide to make the channel box easier to read when setting keys. For example, if you're using FK, you just want to rotate most joints, not move them. Lock and hide the translate and scale channels on the FK control objects, so that when you're animating you only have to see the stuff that matters.