Rotating a 90 degree joint without inflating it I created an L shaped box, and i want to animate it so that it will straighten up, similarly to a clock hands movement. I tried using an armature for this, but wherever i place it, it causes the joint to inflate. I also tried to use a hook modifier, so that some of the vertexes follow an empty's rotation - but had the same result.
You will never get a perfectly straight mesh with this approach. Even if you tweaked the vertex weights so that this case (90deg rotation) looked fine, you would see the limits of it once you start rotating it further.
You could use two different meshes instead, each bound to one bone, or even two different objects, each parented to one bone.