Imposes a maximum triangle area. If a number follows the `a', no triangle is generated whose area is larger than that number. If no number is specified, 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. Each area specified may include a decimal point.