Is it possible to force an object, a child of some hierarchy, to always look down one of the World axes, Y- for example? I already figured a way of doing it with a lookAt object (with blend ObjNode and a single translate axis enabled), but I bet there's a more elegant way of accomplishing this.
Think of a crane with a rope and a hook hanging from the end of its arm. Whenever the crane's arm rotates up or down, the rope always should point downwards, at the ground.

Did you ever find a solution to this? I'm trying to do similar (also modelling a crane actually) and have no idea how to do this.

I'm trying to keep a crane at the origin, and allow the central column of the crane to rotate around the Y-axis.

I'm trying to drive the central rotation of the crane using a box (the object the crane is carrying) in space which moves along a curve, so I want the crane to turn and face the box.

Any ideas?

The look-at constraint chop allows selecting any of the cardinal directions (+/-) for the look-at and look-up axes.

jsmack
The look-at constraint chop allows selecting any of the cardinal directions (+/-) for the look-at and look-up axes.

Thanks but I'm not getting it to work…

In the case of the screenshot, you'll see the y-position of the sphere is zero. I want to be able to adjust the y-position of the sphere, but somehow lock the rotation of the cube as it would be if the y-position of the sphere was zero.

Changing the look-at and look-up axes only seems to flip each axis 180 degrees, so doesn't appear to do what I need.

does this work for you?
I added a Blend Constraint and blended in only the ry from the lookat

arctor
does this work for you?
I added a Blend Constraint and blended in only the ry from the lookat

Perfect! Thanks so much!