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entry variable: $area -- abs name orig area file
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default: $SUBJECTS_DIR/name/surf/$hemi.area

The "area:" entry shows the current filed loaded
as original area.  To load a different original
area file, select one from the "area:" dropdown
and use "R", for example:

 $hemi.area -- standard local area file (white)
 $hemi.area.mid -- area calculated at mid depth
 $hemi.area.pial -- area calculated on pial

The area at a vertex is defined as the sum of 1/3
the area of each adjacent triangular face.

Relative name assumes same dir as above.  Home
dir of subject can be abbreviated as tilde (~).
Absolute name OK, too.  Reads either old area or
new area file format.

Binary oldarea file format:
  [no magic number]
  3-byte uint vertex count
  3-byte uint face count
  4-byte float data [vtx0]
  4-byte float data [vtx1]
  ...
  [implicit vtx numbering -- all vtxs req'd]

Binary newarea file format (=newcurv format):
  3-byte magic number: 16777215
  4-byte int vertex count
  4-byte int face count
  4-byte int values per vertex
  4-byte float data [vtx0]
  4-byte float data [vtx1]
  ...
  [implicit vtx numbering -- all vtxs req'd]

The area files in the entry can be read into the
.origarea field or the .origarea2 field (see
R-click help for "area:" label).
