Problem with shade_volume and the [XYZ]RANGE Keyword

[Ricardo Fonseca <zamb(at)physics.ucla.edu>]

Hi everyone

I'm having a problem with the SHADE_VOLUME procedure and the [XYZ]RANGE
keyword. Whenever I set the range the minimum range to anything other than 0
the resulting isn't the expected isosurface but a set of scattered
polyogons. 

In other words, this works fine:

Data = FltArr(NX,NY,NZ)

shade_volume, data ,isoval, v, p, XRANGE = [0,NX/2]

and this doesn't

shade_volume, data, isoval, v, p, XRANGE = [NX/2,NX-1]

Any suggestions other than feeding shade_volume with a subset of data (i.e.
data[NX/2:*,*,*])?

Thanks in advance, Ricardo