track to problem

Hi all!
I’m using blender 2.25
I’m trying to set up a bone (it’s the ‘head’ bone of a cartoonish mosquito I’m going to animate) to always point at an empty. My goal is to greate a rig that can be controlled by moving null objects (ie. empties) only.
Here comes my problem: when I apply the track to constraint to the head bone and set the target to my null object (in this case head_target) the head bone will point at the null - but at the same time it will roll about 90°

I figured that this problem occurs because the mosquito’s up-axis is set to z while the head bone’s up-axis is x. But I can’t change that it seems. Whenever I rotate the bone to change the up axis it will be displaced. And once I move it back in place the axis is as it was before…

Any idea how to change that?

This is done through the Animation Buttons (F7, or bendy
arrow icon) … you can set ‘track’ and ‘up’ there. Also, don’t
forget to clear rotation on your mosquito head (alt-R).


I discovered those buttons - but they set the axis for the whole armature - the problem is that different bones in there have different orientations…
if I set it up to be correct for the head the legs will look odd :frowning:

Uh oh. I would use 1 chain IK constraints (2 chain if you include the little
null bone) as a workaround.

I think ol’ theeth is working on a fix that will remedy this problem,
but it probably won’t make it into the main blender tree for a little
while yet.


wew that trick worked! thanks so much, I’ve got a working null-based rig now :]

-> it’s easy and fast to animate I hope

Good ol’ theeth has already finished his fix, will commit to Tuhopuu as soon as you tell me how :wink: