Hi Marc, here's a demo of how the "axis manipulation" method works:




The way it works is after you place the initial point, only the z axis is in the plane, pointing along the curve's tangent direction.

So the second step after that is to grab the x axis and pull it around to point at some other spot on the same curve opposite the point you initially placed.

Now there are 2 axis directions in the same plane as the curve, which is good. But now you want to rotate the whole thing so that it is the x and y axes in the plane, not the x and z axes as it currently has.

So to do that, click once (instead of drag) on the x axis, you will see there that the dot shifts to it, that makes it the primary axis. Now you can grab the z axis and drag it to rotate it around the x axis, stop when it does an angle snap in a 90 degree increment.


But yes putting in a circle is less complicated.


But the above may give you more of an idea how the axis orientation picker thing works.


- Michael