Hello,
The Angle component always retrieves the smallest angle, in absolute value, between two vectors, unless you provide it a plane that acts as a polar system to do an oriented measure. If so, the angle is measures from Vestor A to Vector B, both projected on the plane, going anti-clockwise around the Z axis of the plane.
I changed your global plane to a local vertical plane constructed at each point from the tangent to the curve and the world Z axis. However this still gives values between 0 and 2Pi, a Pick'n'Choose is then needed to do the if/then/else procedure that leads to an angle between -Pi and Pi.
I’ve added extra examples if you want to only retrieve positive joints, or do something else based on this criteria.
Have a look at this also If statement on empty branch - #4 by magicteddy
Angle and IF question.gh (17.1 KB)