This is a follow-on task to http://www.google-melange.com/gci/task/view/google/gci2012/7968224

That task implemented support for calculating triangle mesh surface areas, but it didn't correctly implement surface area for "plate mode" triangle meshes.  BRL-CAD supports "sheet metal" style geometry where you merely define a triangle mesh surface and then give it a thickness.

For example, if I had even just a single triangle, I could make that be a plate-mode BOT by defining said thickness.  For the surface area, it then should be the area of the triangle times two (top and bottom), but ALSO the area of three rectangles on the sides.

You'll probably end up running mged and modifying this code:

src/librt/primitives/bot/bot.c

Submit you changes as a single patch file, see http://brlcad.org/wiki/Patches for help.