  Visualization techniques for the decision space of continuous multi-objective
optimization problems (MOPs) are rather scarce in research. For long, all
techniques focused on global optimality and even for the few available
landscape visualizations, e.g., cost landscapes, globality is the main
criterion. In contrast, the recently proposed gradient field heatmaps (GFHs)
emphasize the location and attraction basins of local efficient sets, but
ignore the relation of sets in terms of solution quality.
  In this paper, we propose a new and hybrid visualization technique, which
combines the advantages of both approaches in order to represent local and
global optimality together within a single visualization. Therefore, we build
on the GFH approach but apply a new technique for approximating the location of
locally efficient points and using the divergence of the multi-objective
gradient vector field as a robust second-order condition. Then, the relative
dominance relationship of the determined locally efficient points is used to
visualize the complete landscape of the MOP. Augmented by information on the
basins of attraction, this Plot of Landscapes with Optimal Trade-offs (PLOT)
becomes one of the most informative multi-objective landscape visualization
techniques available.
