Ciao,
questi sono i parametri che vuole:
DisplacementMapFilter(mapBitmap:BitmapData = null, mapPointoint = null, componentX:uint = 0, componentY:uint = 0, scaleX:Number = 0.0, scaleY:Number = 0.0, mode:String = "wrap", color:uint = 0, alpha:Number = 0.0)
Initializes a DisplacementMapFilter instance with the specified parameters.

Quì te li spiega:
alpha : Number
Specifies the alpha transparency value to use for out-of-bounds displacements. DisplacementMapFilter
color : uint
Specifies what color to use for out-of-bounds displacements. DisplacementMapFilter
componentX : uint
Describes which color channel to use in the map image to displace the x result. DisplacementMapFilter
componentY : uint
Describes which color channel to use in the map image to displace the y result. DisplacementMapFilter
constructor : Object
A reference to the class object or constructor function for a given object instance. Object
mapBitmap : BitmapData
A BitmapData object containing the displacement map data. DisplacementMapFilter
mapPoint : Point
A value that contains the offset of the upper-left corner of the target display object from the upper-left corner of the map image. DisplacementMapFilter
mode : String
The mode for the filter. DisplacementMapFilter
prototype : Object
[static] A reference to the prototype object of a class or function object. Object
scaleX : Number
The multiplier to use to scale the x displacement result from the map calculation. DisplacementMapFilter
scaleY : Number
The multiplier to use to scale the y displacement result from the map calculation. DisplacementMapFilter

E' molto difficile e a volta anche io mi perdo un po. Ti consiglio di fare delle prove cambiando i valori per vedere i risultati ottenuti e fare le tue conclusioni.

A volte è più semplice da fare che da spiegare...