calculate fmask. Economize memory (we do not need to keep fmask anymore)
fmask
Utilities
result = fmask()
Return value
A 3d array corresponding to fmask.
Examples
Used like if fmask was a known array by substituing fmask by (fmask())
For example: Instaed of write fmask[domainef] we have to write (fmask())[domainef]