In EnergyPlus, what is the reason for having the same number of receiving points as sides on a receiving surface? And what is the reason for placing the receiving points "inside" the surface, and not just at the corner points? Is it to save calculation time that the receiving surface is not divided further? By moving the receiving points inwards, I recon it ensures that less surface area is considered shaded, if rays from a receiving point does not reach the sky.