Reference:Spherical Pattern

The spherical pattern creates a one unit radius sphere, with its center at the origin. It is computed by: value = 1.0-min(1, sqrt(X^2 + Y^2 + Z^2)) It starts at 1.0 at the origin and decreases to a minimum value of 0.0 as it approaches a distance of 1 unit from the origin in any direction. It remains at 0.0 for all areas beyond that distance. This pattern was originally created for use with halo or media but it may be used anywhere any pattern may be used.