While playing around with 2D quadratic splines of a trajectory, I sometimes perceive the resulting curve rotating "in 3D" when changing the parameters. Here is a crude GIF example:
And another example. (The jerks are due to my poor video editing).
INTVis the difference in the parameter t between each pair of consecutive points.
DIR_Yare the initial slopes in each coordinate.
Why is this so? Is there any mathematical explanation of this phenomenon?
edit. If it's of any use, I can provide the source of the program.