First prototype of a widget to edit 3d rotation via a 2d plane. The 3 buttons below the gradient allows plane selection ( XY, YZ or ZX ).
The black area in the Y axis is a constrain ( between 90° and 270° ).

Still a lot of stuff to be done, like the processing of the shortest path (it is wrong from time to time) + better transition of the gradient (the constrains are glitching when animated…).