If a number follows the `a', no triangle will be generated whose
area is larger than that number. For instance, -a2.5 specifies
that no triangle should have area greater than 2.5.
If no number is specified after the `a', an
.area file (if
-r is used) or
.poly file (if
-r is not used)
specifies a set of maximum area constraints.
An .area file
contains a separate area constraint for
each triangle, and is useful for refining a finite element mesh
based on a posteriori error estimates.
A .poly file can optionally
contain an area constraint for each segment-bounded region, thereby
controlling triangle densities in a first triangulation of a PSLG.
You can impose both a fixed area constraint and a varying area constraint
by invoking the -a switch twice, once with and once without a
number following.