The r2stl function generates STL files. The command
is:
r2stl(x, y, z, filename = '3d-R-object.stl', object.name = 'r2stl-object',
z.expand = FALSE, min.height = 0.008, show.persp = FALSE,
strict.stl = FALSE)x, y and z should be
vectors of numbers, exactly as with R’s normal persp()
plot. x and y represent a flat grid and
z represents heights above this grid.
filename is pretty obvious, I hope.
object.name The STL file format requires the object
that is being described to have a name specified inside the file. It’s
unlikely anybody will ever see this, so there’s probably no point
changing it from the default.
z.expand By default, r2stl() normalizes
each axis so it runs from 0 to 1 (this is an attempt to give you an
object that is agnostic with regard to how large it will eventually be
printed). Normally, the code then rescales the z axis back down so its
proportions relative to x and y are what they were originally. If, for
some reason, you want your 3D plot to touch all six faces of the
imaginary cube that surrounds it, set this parameter to
TRUE.
min.height Your printed model would fall apart if
some parts of it had z values of zero, as this would mean zero material
is laid down in those parts of the plot. This parameter therefore
provides a minimum height for the printed material. The default of 0.008
ensures that, when printed, no part of your object is thinner than
around 0.5 mm, assuming that it is printed inside a 60 mm x 60 mm x 60
mm cube. Recall that the z axis gets scaled from 0 to 1. If you are
printing a 60mm-tall object then a z-value of 1 represents 60mm. The
formula is min.height = min.mm / overall.mm, so if we want a minimum
printed thickness of 0.5mm and the overall height of your object will be
60mm, 0.5/60 = 0.008, which is the default. If you want the same minimum
printed thickness of 0.5mm but want to print your object to 100mm, this
parameter would be set to 0.5/100 = 0.005.
show.persp Do you want to see a persp()
plot of this object on your screen as the STL is being generated?
Default is FALSE.
strict.stl To make files smaller, this code cheats
and simply describes the entire rectangular base of your object as two
huge triangles. This seems to work fine for printing, but isn’t strictly
proper STL format. Set this to TRUE if you want the base of
your object described as a large number of triangles and don’t mind
larger files.
To view and test your STL files before you print them, you can use
various programs. I have had good experiences with the free, open-source
Meshlab, which even has iPhone and Android versions so you can let
people interact with your data even when you’re in the pub. Even if all
you ever do is show people your 3D plots using Meshlab, I believe
r2stl() still offers a useful service, as it makes viewing
data far more interactive than static persp() plots. To
actually get your hands on a printer, you might try your local school -
apparently lots of schools have got rapid prototypers these days.