This modifier draws particles along the spline by a series of circular 'handles' which exert various forces.
When a spline is placed in the modifier, five handles are automatically created, which appear as child objects in the Objects Manager; these can be deleted or duplicated to reduce or increase the handle count.
Each handle has its own settings for position, size (Distance) and the various forces it can exert on particles.
These settings are accessed by selecting a handle in the Objects Manager.
They are explained further down the page.
There are also global controls for the various forces which can be accessed via the modifier’s Object tab.
xpSplineFlow General tab settings.
Checking this box activates xpSplineFlow.