stlwrite - write ASCII or Binary STL files

** Big speed boost courtesy of Oliver Woodford. Recommended to update to latest version **
stlwrite(FILE, FV) writes a stereolithography (STL) file to FILE for a
triangulated patch defined by FV (a structure with fields 'vertices'
and 'faces').

stlwrite(FILE, FACES, VERTICES) takes faces and vertices separately,
rather than in an FV struct

stlwrite(FILE, X, Y, Z) creates an STL file from surface data in X, Y,
and Z. stlwrite triangulates this gridded data into a triangulated
surface using triangulation options specified below. X, Y and Z can be
two-dimensional arrays with the same size. If X and Y are vectors with
length equal to SIZE(Z,2) and SIZE(Z,1), respectively, they are passed
through MESHGRID to create gridded data. If X or Y are scalar values,
they are used to specify the X and Y spacing between grid points.

stlwrite(...,'PropertyName',VALUE,'PropertyName',VALUE,...) writes an
STL file using the following property values:

MODE - File is written using 'binary' (default) or 'ascii'.

TITLE - Header text (max 80 chars) written to the STL file.

TRIANGULATION - When used with gridded data, TRIANGULATION is either:
'delaunay' - (default) Delaunay triangulation of X, Y
'f' - Forward slash division of grid quads
'b' - Back slash division of quadrilaterals
'x' - Cross division of quadrilaterals
Note that 'f', 'b', or 't' triangulations now use an
inbuilt version of FEX entry 28327, "mesh2tri".

FACECOLOR - Single colour (1-by-3) or one-colour-per-face (N-by-3)
vector of RGB colours, for face/vertex input. RGB range
is 5 bits (0:31), stored in VisCAM/SolidView format
(http://en.wikipedia.org/wiki/STL_(file_format)#Color_in_binary_STL)

Example 1:
% Write binary STL from face/vertex data
tmpvol = false(20,20,20); % Empty voxel volume
tmpvol(8:12,8:12,5:15) = 1; % Turn some voxels on
fv = isosurface(~tmpvol, 0.5); % Make patch w. faces "out"
stlwrite('test.stl',fv) % Save to binary .stl

Example 2:
% Write ascii STL from gridded data
[X,Y] = deal(1:40); % Create grid reference
Z = peaks(40); % Create grid height
stlwrite('test.stl',X,Y,Z,'mode','ascii')

Example 3:
% Write binary STL with coloured faces
cVals = fv.vertices(fv.faces(:,1),3); % Colour by Z height.
cLims = [min(cVals) max(cVals)]; % Transform height values
nCols = 255; cMap = jet(nCols); % onto an 8-bit colour map
fColsDbl = interp1(linspace(cLims(1),cLims(2),nCols),cMap,cVals);
fCols8bit = fColsDbl*255; % Pass cols in 8bit (0-255) RGB triplets
stlwrite('testCol.stl',fv,'FaceColor',fCols8bit)