To alleviate the issues of the Das-Dennis method, an energybased approach has recently been proposed 43 in the multiobjective optimisation literature. Inspired by methods in physics, a generalisation of the potential energy called the Riesz s-energy is calculated for a given number of reference points on the unit simplex. The Riesz s-energy U s is defined between two points (c) NSGA-III Fig. Visualisation of the splitting front procedure of non-dominated sorting genetic algorithms: (a) The Pareto dominant front is shown in dark blue, the splitting front is light blue, and the remaining solutions are white. For this example, the second front is chosen as the splitting front, and it is assumed that five more solutions need to be picked to complete the population. These solutions will be indicated with a dark blue circumference. (b) The selection procedure of NSGA-II calculates a distance in objective space to the nearest neighbours in the front. The outermost solutions are picked by default, the remaining solutions are chosen according to the furthest distance from neighbours. (c) The selection procedure of NSGA-III calculates the orthogonal distance to predefined reference directions in objective space and selects the closest solution for each axis. Note that the two objective axes are also used as reference directions so that the outermost solutions are picked by default.