Convert 3D coordinates to stl surface

So I have an issue from coordinate data[X,Y,Z]. It appears you can use stlwrite to readily convert vertice and face data or X,Y 2D delaunay triangulated graphs to stl files however, since I only have coordinate data [X,Y,Z] I cannot convert the delaunay triangulated object to an stl file because the delaunay functions convert it into tetrahedron instead of a 3D surface. Is there any solution to generate a surface from XYZ coordinate data and export out as an STL file? I cannot seem to find a solution unless there is already facet and vertice data.

Edit: Looks like boundary facets can give me what I'm looking for

Current implementation

X = table(:,1)

Y = table(:,2)

Z = table(:,3)

tri = delaunaytriangulation(X,Y,Z);

stlwrite(tri, 'filename.stl','ascii')

[darova]

Please attach your data

[Bewler]

Here's the data.

I can seem to do

tri = delaunay(X,Y);
trisurf(tri,X,Y,Z);

and it comes out perfectly with heights and transitions and faces between the triangles...

When I try to plot it as an stl, the faces are very incorrect however the coordinate data is correct

tri = delaunay(X,Y,Z);
stlPlot(dataTable,tri, 'stlplot')

Answer 1

[Fabio Freschi]

I don't know where the stlPlot function comes from, so I cannot replicate your problem. Anyway, your call

tri = delaunay(X,Y,Z);

Creates a delaunay triangulation with 3d simplexes, e.g. with tetrahedra (four-node volume elements). Maybe this is why you get the wrong result.

[Bewler]

So my current code actually uses

tri = delaunay(X,Y);

and

trisurf(tri,X,Y,Z);

and the result is

Is there no way to convert tedtrahedron into an stl file? I assume tetrahedrons are the mesh that most 3D CAD programs use in FEA so that form of a converted file may work as well rather than an stl. I also don't quite understand the nodes (3 vs 4) and faces(connectivity lists) and how the stl builds from these lists.

[Fabio Freschi]

You can get the surface faces of the tetrahedra with

% tet delaunay
tri = delaunayTriangulation(X,Y,Z);

% get surface faces and nodes
[F,P] = freeBoundary(tri);

% plot with trisurf
figure
trisurf(F,P(:,1),P(:,2),P(:,3),'FaceColor','red');

% or use patch
figure
patch('Faces',F,'Vertices',P,'FaceColor','red');

[Fabio Freschi]

In your case it is maybe better to triangulate the surface in the xy plane

% triangulate in xy
T = delaunay(X,Y);

% create triangulation in 3d
tri = triangulation(T,X,Y,Z);

% plot
patch('Faces',tri.ConnectivityList,'Vertices',tri.Points,'FaceColor','red')

% now save
stlwrite(tri,'mytriangulation.stl');

[tar abu]

hey

can you please send me the stl file.

i need it in "nameofthefile.stl"

thank you

Answer 2

[darova]

I took your data and did this:

A = xlsread('data.xlsx');
X = A(:,1);
Y = A(:,2);
Z = A(:,3);
stlwrite('file.stl',X,Y,Z)
fv = stlread('file.stl')

patch(fv,'FaceColor',       [0.8 0.8 1], ...
          'EdgeColor',       'none',  ...
          'FaceLighting',    'flat',      ...
          'CDataMapping',    'direct',    ...
          'AmbientStrength', 0.5);
camlight
axis equal

Is it wrong?

[Bewler]

So when I try that code it says

Error using stlwrite (line 25)

Input argument must be a triangulation object.

Anyhow, this is what I'm looking to generate in an stl file

[darova]

I downloaded stlwrite() from HERE

[Bewler]

It says patch doesn't have enough input arguments. I'm still trying to see the stl file.

Answer 3

[FRANCESCO OTTAVIANI]

This code worked in my case

clear global;

A = readmatrix('point3d.txt');

B = unique(A,'rows');

X = B(:,1);

Y = B(:,2);

Z = B(:,3);

% triangulate in xy

T = delaunay(X,Y);

% create triangulation in 3d

tri = triangulation(T,X,Y,Z);

% plot

patch('Faces',tri.ConnectivityList,'Vertices',tri.Points,'FaceColor','red')

% now save

stlwrite(tri,'point3d.stl');