The spiral effect changes the placement of the dots in a spiral motion around the center.
Setting the slider to a
negative value will rotate the dots counter-clockwise, a positive
value will rotate them clockwise. A setting of -100% or 100% will
rotate the outmost dots 360° though it may be possible these dots
are not entirely visible on the render due to scale settings.
Please note that with high settings, dots will start to "pack" together.