FlaringIndex
This parameter has to be used
together with AspectRatio. If it is
defined to a value B, while
AspectRatio is defined to a value h0,
then the disk aspect ratio is defined everywhere by:
H/r = h0 * rB
FlaringIndex defaults to 0,
which means a uniform disk aspect ratio or, differently said, a local
disk thickness proportional to the radius ("flat" disk).