The accepted spherical water model is converted to a TIP3P explicit water, and its orientation is chosen by calculating the energy of a pre-calculated set of 9897 uniformly distributed orientations . These energies are used to calculate the probability p j of each orientation based also on in eq.1. Once an orientation is accepted, the grid maps are updated to include the information of the newly added water, and its APs are added to the pool of anchor points.