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
it may be used anywhere any pattern may be used.