action constraints

Hi all,

I’m not much on rigging, but I have to build some bird wings and animate them. After looking at a few of the tutorials I decided to use action constraints because it was the only thing I could really understand (but not entirely, thus this post).

When I am creating the action, can I pose the bones in 3d space, by this I mean can they be rotated and moved in all three directions?

The reason I ask, is because when I look at the action in the action window it looks fine, but when the action constraint is used the action is different. I’ve checked that the constraint setting are all the same for each bone.

What am I missing?

An action constraint is just a way of applying an animation (or action, as it’s called in Blender. Throughout this post, wherever you see the word animation you can substitute it with the word action).

Normally, for example, you’ll create an animation by inserting keyframes for the various bones (for objects with an armature) and for the objects (that don’t have an armature). Then you hit ANIM and ooh and aah.

An action constraint just allows you to use that animation as part of another, larger animation.

One animation may be of the wing folding.
Another might be of the wing swiveling back, up, and forward to grab air, then thrusting down to push air.

When you use an action constraint, you have a little bone off to the side somewhere which indicates how far through that animation you are by its rotation angle. For example, angle 0.0 could be wing in normal position, and angle 90.0 could be completely folded. Angle 45.0 would then be halfway through the ‘folding’ animation. Another little bone off to the side somewhere could be similarly used for the ‘flapping’ animation.

An important thing is to keep the ‘little bones off to the side’ (action constraint targets) in an orthogonal view before rotating them. Otherwise rotating will have less than the desired effect.

To answer your post, yes, you can pose the bones any way you like in 3D space, just as in any other animation.


[ ] each action has a good (descriptive) name
[ ] the values for an action constraint allow full range of motion
    - min and max are set to something like [-90, 90] or [0, 90] or [90, 0] (as appropriate)
    - start and end are set to the first and last frame of the named action
    - rotation axis is set to the appropriate axis. For example, if you want to 
      look at the action target bone from the front view when manipulating it,
      set the axis to Z.
[x] all bones with an action constraint targeting the same bone have the same values
[ ] you only rotate the action target bones from front/side/top (as appropriate) view.

Hope this helps.

Douas, why the little “x” in just one of those check boxes? (the only one I didn’t understand by the way)

I think your previous tutorial on actions is one of the best to get a grip on what they are and how they are applied:

I don’t know if much has changed from this in the new system other than some terrific UI improvements and the way actions are played within the NLA. As far as I can tell, the fundamentals are still the same so it would still be a worthwhile tute to read.

Maybe an update is needed :wink:

Hmm, I don’t remember. Perhaps I just have to do something random now and then…

If I figure it out I’ll post. Thanks for the link.