2D Armature

I’m trying to figure out how you’d go on about making an armature constricted to 2 dimensions (x and y) with IK. I’ve tried adding rotation limitation constraints to the bones, only allowing them to rotate round Z, but the bones start behaving funky if I do (together with IK). I found this video on vimeo:

So I know it’s possible. In the video the bones somehow seem to be constricted to 2 dimensions automatically for some reason. If I try doing what he does in the video, the bones will start going “upwards” if the IK handler gets too close, to solve the constraint. (See the attached file.)

Preferably, I’d like to use Auto IK if it’s possible to do so with a 2 dimensional armature.

Any help please?

Attachments


That should work, and it does for me (in both regular and Auto IK). Have you made sure that all your bone axes are aligned with Z perpendicular to the plane?

Best wishes,
Matthew

Please have a look at this video. This is what I’m experiencing:

That all looks OK to me. The bones are staying in the plane, as required, not popping up out of it as suggested by the image in your first post. There’s some angle flipping as you go past directly up-and-down, but that’s normal behaviour for IK with straight-line bones and no pole target.

What exactly did you expect to be different?

Best wishes,
Matthew

I expected the bones wouldn’t flip. The movement seems to be a lot more smooth in the vimeo tutorial. But maybe that’s the way it has to be. :confused:

Also, is there an easier way to add these limit rotation constraints, than to do it manually for each newly added bone? That’s gonna get tedious fast.

edit:
Wow, please download this:
http://dl.dropbox.com/u/608462/wtf.blend

Showhow I managed to constrain the rotation of the left bone structure without adding any constraints. When trying to do the same thing again with the right bone structure, it did of course not work. Do you have any idea what differs these two armatures?

That tutorial uses a second IK target to stop the flipping, effectively equivalent to a pole target.

Also, is there an easier way to add these limit rotation constraints, than to do it manually for each newly added bone?

If you use actual IK constraints rather than auto, you can use the Lock Rotation buttons in the Armature Bones panel, which is easier than adding a separate constraint, but still has to be done for each bone. Either way, a script might be a reasonable solution for a large armature.

Best wishes,
Matthew

In the left one, all the bones have their Z axis correctly aligned; in the right one, the root bone is twisted. Set the bone roll to 0 in edit mode, then clear the pose. It should then work like the left one.

Best wishes,
Matthew

Thanks for clarifying and for your time, MCollett. :slight_smile:
Now I understand.

(So the main problem was that the bones weren’t aligned correctly. They were this because of how a bone is added when you create an armature. There is a default bone going straight up, and of course I couldn’t accept that, so I’d drag it out making it straight-looking. Apparently it wasn’t. Now I always remove all the bones in edit mode first, then add a bone from top view. That way, it and all the bones I extrude are aligned correctly from the beginning, and there aren’t any bones poking me and being annoying.)