stlwrite - Write binary or ascii STL file

Export a variety of inputs (patch, surface) to an STL triangular mesh

Description

** 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 = zeros(20,20,20); % Empty voxel volume
      tmpvol(8:12,8:12,5:15) = 1; % Turn some voxels on
      fv = isosurface(tmpvol, 0.99); % Create the patch object
      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')

  Original idea adapted from surf2stl by Bill McDonald. Huge speed
  improvements implemented by Oliver Woodford. Non-Delaunay triangulation
  of quadrilateral surface courtesy of Kevin Moerman. FaceColor
  implementation by Grant Lohsen.

Note: This entry was originally titled "patch2stl", however has been renamed to "stlwrite" after more general input was added.

Acknowledgements

Surf2stl and Mesh2tri inspired this file.

This file inspired Stlwrite Write Binary Or Ascii Stl File.

• MATLAB release: MATLAB 7.13 (R2011b)

[Ben]

Very nice code and amazing fast! Thanks for sharing!

[JD]

@Sven: Thanks. It worked like a charm! It didn't work when I tried to connect it with using triangulation in stlwrite but when I used used mesh2tri to generate the faces and vertices and then used those in stlwrite, it worked! Thanks a lot again for such a quick reply!

[Sven]

@JD:
The issue is that your input is "gridded data" not "triangulated data" because each of x, y, z is a 20-by-20 matrix, rather than a set of vertices and triangles.
This can be handled by stlwrite (see the help file for the "triangulation" parameter), but you'll need to understand that the default "triangulation" of gridded data is a delaunayTri of the X-Y 2D data. In this sense you have repeated X-Y pairs (one at the top of the sphere, one at the bottom). The warning you're getting comes from "delaunay", not from "stlwrite".
You can overcome this by specifying how you want your gridded data triangulated:

stlwrite('test1.stl',x,y,z,'mode','ascii','triangulation','f')

Note that you'll need "mesh2tri" from http://www.mathworks.com/matlabcentral/fileexchange/28327 for this to work. I will ask Kevin for permission to include it in stlwrite (it's a small but very handy function) for a next release.

[JD]

Hi! I am facing the same issues as Alexandra. I was trying to gererate surface mesh for a sphere and then converting into .stl format. When I tried to view it in Meshlab, one half of the sphere was gone. I did get a warining about duplicate data points.

Warning: Duplicate data points have been detected and removed.
Some point indices will not be referenced by the triangulation.

The commands I used are below:
[x,y,z]=sphere(20);
stlwrite('test1.stl',x,y,z,'mode','ascii');

Any help will be highly appreciated. Thanks.

[Sven]

@Alexandra, I'll bet that probably there are some duplicated/disjoint vertices in MATLAB prior to using stlwrite. Can you send me an example of the data that is coming through open?

[Alexandra]

Hej,
I have the problem that I get open surfaces after using STLwrite. Has anybody an idea what to do about this?

[or litany]

does anyone know how to show the different colors per face I used? I've tried meshlab and 3d max

[Adam]

Thanks for your help Sven, turns out the problem was in my import settings in Gambit. It needed to be a little different because of the more complex geometries in those files. Again, wonderful program!!

[Sven]

Ha, that last message was from me - logged on from another computer at work.

[Binu]

@Nick and Adam, I'm not sure what issues may be at play with your files. Feel free to email a .mat file with your points/faces data *and* the 2 or 3 lines you use to create a working(!) figure from this data in MATLAB (note that I'll only have time to look at it if the figure creates cleanly).

[Adam]

Great program. It worked fine for 2 of my files with relatively simple geometries, but one other didn't output a readable mesh (I tried to open it in both Solidworks and Gambit), the other didn't connect the mesh into triangles, there were just some points in Gambit. Both mesh just fine using the trimesh function. Any ideas?

[Nick]

@Sven you've been very clear, thanks. i ask an other question, to better understand.

my set of p x-y-z describes a 3D surface that i can see properly in matlab (using plot3 or trisurf), as you say.

to write the stl, I can use directly the function "stlwrite"?
Does this make a triangulation of my 3D coordinates?

In that case, which options I have to give to the function to make it works properly? because I have tried many ways, but when i give 'triangulation' it wants other options and values, and I don't know what to put into.

thanks again!

[Sven]

@Nick: If you create a Delaunay triangulation from a set of p X-Y-Z points:

dt = DelaunayTri(x,y,z)

The result (dt.Triangulation) will not be a "triangular surface mesh". You'll notice that the result is an n-by-4 matrix. This means that each row in the triangulation represents a tetrahedron - a small *solid* with 4 triangular faces - not a surface triangle.

STL format describes surface triangles rather than tetra solids. Perhaps you want the convex hull of your points? (ie, only the *outermost faces* of all of your tetra solids) Note this will only work if your simple solid body is in fact convex.

Here's my advice: plot to the screen before trying to write to an STL file. If you can get a 3d surface plot (using patch, trisurf, etc) working in MATLAB first, *then* you will be able to write to STL without problems.

[Nick]

hi, I have a set of coordinates of a simple solid body, and I have to create finite volumes to work on. So I made a 3D Delaunay triangulation, and I have now a n-by-4 matrix with the points of resultant tetrahedron. Now, I need to create a .stl file to export this work. how do I do this? Is it possible? Because in the option There is only the voice for a triangulation in 2D. Thanks a lot.

[Joachim]

 

[Romain W]

 

[Sven]

@ava: glad to hear that the issue (nodes indices) was resolved

[ava]

@Sven:I am using STL viewer and also MiniMagics 2.o to see the result file but all the faces are disconnected.

[Sven]

@ava: This is the first I've encountered such an issue. Does the same thing happen when you run the example in the stlwrite help? If not, try using the splitFV FEX entry to see if the original faces/vertices are indeed connected. If the stlwrite example itself comes out unconnected, what software do you use to read the .stl?

[ava]

Faces are not connected in the result stl. ,Does anyone have any idea?

Thanks

[William Thielicke]

Works nicely. For my old Matlab version, I had to remove one line to make it work:
narginchk(2, inf)

[Oliver Woodford]

Binary output is now very fast! :)

[Sven]

@Oliver
The latest update has made significant speed improvements with vectorised face normal calculation and combining adjacent fwrite calls. Hope it's useful.

[Oliver Woodford]

Works well, though very slow (in binary mode at least).

[Holger Roth]

Great! That's what I looked for...

[Georg Stillfried]

Worked fine!

[Scott Burnside]

Nice companion to cad2matdemo.m. Very useful.