The Displace filter applies distortion according to a pattern defined by a displacement map. The lightness values of pixels within the displacement map determine the degree to which the distortion occurs.
About the Displace filter
The displacement map used to create the distortion can be either from an external file or from layers directly beneath the layer to be edited. For the former, the Internet offers many displacement maps to download and try out. For the latter, the displacement effect works with your existing layer content, typically blending sympathetically with the underlying background texture. This filter can be applied as a non-destructive, live filter.
Settings
The following settings can be adjusted on the vertical slider:
Strength—sets the intensity of pixel displacement. Negative values shift pixels upwards, positive values shift pixels downwards.
Opacity—sets how visible the filter is, e.g. at 1% opacity the filter effect is almost transparent whilst at 100%, it is fully opaque.
The following settings can be adjusted on the context toolbar:
Beneath—determines the displacement map using layers beneath the selected layer.
Load Map from file—allows for using one own's images as the basis for pixel mapping.
Scale To Fit—when enabled, the displacement map stretches or shrinks to fit the document size. If disabled, the displacement map retains its native dimensions.
Method
Red/Green—edge detection based on pixel values and the amount of specified colour.
Sobel 3x3—edge detection based on 3 by 3 kernel convolution. This method is preferable if you would like to maintain the effect's position. Apply this method before loading the displacement map image.
Split—when toggled, it allows for a before and after preview mode.
Merge—applies modifications set by parameters and settings to layers below.
Reset—rejects and resets filter adjustments to their starting position.
Protect alpha —allows to control how the edges of a filter behave, e.g. they can be hard, to separate the effect from another object or background. Soft edges, on the other hand, would give a more calmer and stable transition.