20.11.2016, 16:31
A negative angle does not "revert" the direction, that in fact only works for 90°. This operation changes a clockwise angle to counter-clockwise, which is something different.
You can add or substract 180.0 to/from the angle to make it face the opposite direction.
You can add or substract 180.0 to/from the angle to make it face the opposite direction.