Controlling IK up axis?

[Anonymous]

I tried my best to find a specific tutorial that helped me out years ago, but that was a failure. So here I am again.

I have a robot arm I am controlling with IK. It has quite a few joints. In Maya, you can just lock an axis, and it won't use it in the IK. But in Max that doesn't seem possible. Locking them just means you can't directly rotate them. IK still does.

Each joint can only rotate in one axis, but the IK doesn't know that.

I thought there was a way of adding an object to each and telling Max that was the joint's UP. But I can't, for the life of me, find that anymore. And searching has become increasingly difficult over the years because there's so much more garbage out there now. 

Right now, the base joint tilts slightly. I need to stop that tilt. When I added some sort of constraint (not sure what) defining it's up axis, that was fixed. But that was years ago, and on a different model.

[leeminardi]

Create  a point whose position is controlled by a wire parameter or expression controller that is referenced by the IK Solver.  For example, you could have a point above the shoulder and its x and y coordinates are equal to the x and y coordinates of the upper arm pivot point.  Make that point the target for the IK Solver plane.  If this is not clear post a file of the robot.