Jagadish,
| I have 8 viewports in my plot which has worked well. But once in a
| while, apparently at random for some plots, about lower half of the
| viewport located at the lower right corner is blank.
I occasionally see similar problems and I have the feeling that that
is a bug in the contouring routine of Ferret. I don't know if there
is a systematic workaround.
If you first SHADE and then FILL, you may get something looking
tolerable:
shade/lev= . . . var
fill/lev/ov var !! use the same levels.
Regards,
Ryo