varyStepDirection [boolean]:
If true, introduced for every optimization process a noise term by which points will be shifted (on their circle). See Eq. 4 in [1].
If false, there will be no noise term which might lead to artifacts, especially in case of OptimizationType.DISCRETE.
In that case and with {@link AttributesOSM#movementType} not DIRECTIONAL, the first point of each circle will at (r * cos(0), r * sin(0)).