The displacement is used when the lines overlap and/or are close to each other at the current level of detail. In general, displacement methods move the conflicting features apart so that they do not interact and can be distinguished.

This module implements an algorithm for displacement of linear features based on the Snakes approach. This method generally yields very good results; however, it requires a lot of memory and is not very efficient.

Displacement is selected by method=displacement.

It uses the following parameters: * threshold - specifies critical distance. Two features interact if they are closer than threshold apart. * alpha, beta - These parameters define the rigidity of lines. For larger values of alpha, beta (>=1), the algorithm does a better job at retaining the original shape of the lines, possibly at the expense of displacement distance. If the values of alpha, beta are too small (<=0.001), then the lines are moved sufficiently, but the geometry and topology of lines can be destroyed. Most likely the best way to find the good values of alpha, beta is by trial and error. * iterations - denotes the number of iterations the interactions between the lines are resolved. Good starting points for values of iterations are between 10 and 100.

The lines affected by the algorithm can be specified by the layer, cats and where parameters.