If Spacing is NaN, there is no minimum spacing, allowing nodes to overlap, unless Radius is NaN, in which case the effective spacing will be 6 to determine an effective radius. If Spacing is a number but Radius isn't, the effective spacing will be Spacing, and this will determine the effective radius. If both Spacing and Radius are numbers, the effective radius will be at least Radius, but may be larger so that the minimum spacing between nodes is Spacing.