Piston misbehaving


Could someone please point me where I’ve gone wrong with the rigging on my droid? There is an empty box which is supposed to be used for moving the whole thing but I’ve messed up somewhere. When the box is moved, everything else moves but the upper piston arm is tracking to something invisible :s

mediBot.blend (684 KB)

Change the Track To constraint on mainHyd_topTube to track World Space>World Space.

That said, you might have an easier time of all this with an armature instead. Bones’ tracking behavior is often a bit easier to predict and comprehend than the same constraint on a mesh object.

Hey thanks!

Yeah I’m still new to rigging, not even touched on bones yet. (sounds rude). But I’ll give it a shot soon. I’m still confused as to the local to local - world to world space.

As I understand it, Local Space is looking for the tracking target to change its position directly. When it is moved along with everything else, its position doesn’t change relative to the thing trying to track it. So as far as the Track To constraint knows, that Empty hasn’t really moved. With World Space, the constraint will look for any change of position relative to the whole scene.

Another way to think of it is this: Imagine you have a rock sitting on the surface of a planet. In Local Space (just looking at its position relative to the planet), it is sitting perfectly still. But the planet is orbiting the sun, so in World Space (relative to the whole solar system), it is moving in an elliptical path at 70,000 miles per hour.

Yeah that’s a good description, but what does it do when you select local to world
or local to local
or world to local
or local to world?

It does crazy things.

In fact, World to World will also do crazy things, mainly because mesh object rotations don’t work the same way as armature bone rotations. Your setup will still break in some poses, particularly if you try to rotate the whole assembly. World>Local and Local<World are so rarely useful that you shouldn’t even bother considering them. Right now I’d recommend that you step back from this for a day or two and work through a few basic armature rigging tutorials so you can learn how to do this with bones. There are several good ones out there on rigging pistons as well, so you should be able to rig this up with an armature pretty easily and see much better results.

Context of track to’s
LocalAndWorld.blend (539 KB)

A man stands on the the ground that orbits a sun
One arm follows a ball he is throwing - tracks to - local to local
Around the sun another body is orbiting independently
The other arm points to that body - tracks to - local to world

Play with the track to context and watch weird stuff happen

Hope this helps, or if it does not help, at least it is fun


Thanks martin