Reference:Boxed Pattern

The boxed pattern creates a 2x2x2 unit cube centered at the origin. It is computed by: value =1.0- min(1, max(abs(X), abs(Y), abs(Z))) It starts at 1.0 at the origin and decreases to a minimum value of 0.0 as it approaches any plane which is one unit from the origin. 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.