Well the objects could be moving in any direction. Although in practice this probably not be the norm.
The yellow lines indicate the parallel lines at the time the angle() (redline) was taken.
The yellow lines would be the axis, or slope where other objects would be created.
Then their angles would be set to the offset of the other objects axis. A perpendicular of the parallels.
This also lets projectiles go toward the object, but not to it.
Possible ai to get behind the object.
But yeah, looks like the sin cos method would be best.
Thanks guys.