The location of the points along of the unit simplex are then optimised to minimise the combined Riesz s-energy of all the reference points. This allows for the construction of an arbitrary number of well-spaced reference directions. The results in this paper were obtained using the Riesz s-energy method to generate the reference directions for NSGA-III, with s equal to the square root of the number of objective functions as suggested in the original paper .