Generating STL from vertices and thickness?

I want to generate a .stl file of the shape shown in the image. I define the shape using a set of vertices, which define a 2d polygon, and a thickness which makes it 3d. I have tried a few methods but haven't had any success in generating .stl file similar to the one I need.

Answer 1

[KSSV]

If you have vertices and nodal connectivity matrix in hand, use this to write to .stl file. https://in.mathworks.com/matlabcentral/fileexchange/20922-stlwrite-filename--varargin-

Answer 2

[DGM]

If you have the boundary vertices of one of the profiled sides, the rest is relatively simple. For such a simple part, it's easy enough to manually triangulate the surface, or you can use delaunayTriangulation().

% you have some vertices defined in a CCW path around the object boundary
V = [0 0 0; 1 0 0; 1 2 0; 6 2 0; 11 0 0; 11 1 0; 6 3 0; 1 3 0; 1 5 0; 0 5 0];
th = 0.4; % and you have some thickness

% either you can just manually define the triangles on the top side ...
%F = [1 2 3; 4 5 6; 1 3 10; 3 8 10; 8 9 10; 8 3 4; 8 4 7; 4 6 7];

% ... or you could do a constrained triangulation to generate them.
nverts = size(V,1);
E = [1:nverts; circshift(1:nverts,-1)].';
T = delaunayTriangulation(V(:,1:2),E);
F = T.ConnectivityList(isInterior(T),:);

% create the back side faces and vertices
nverts = size(V,1);
V = [V; V]; % duplicate (x and y stay the same)
V(1:nverts,3) = th; % establish z-offset between the two sets of faces
F = [F; fliplr(F) + nverts]; % flip the winding and offset the indices

% since our object is two parallel surfaces with the same number of
% boundary vertices (in the same order), we can just stitch those together.
% va is just a right-handed progression of the boundary vertices (in a column vector).
% in this case, our boundary vertex list is a simple linear sequence.
va = reshape(1:nverts,[],1); % front
vb = va + nverts; % back
vc = circshift(va,-1); % front
vd = vc + nverts; % back
F = [F; va vb vc; vd vc vb]; % add them to the list

% write to file
stlwrite(triangulation(F,V),'testfile.stl')

% display it using patch()
patch('faces',F,'vertices',V, ...
    'facecolor','w','edgecolor','k');
view(3); camlight; view(10,33)
axis equal; grid on
xlabel('X'); ylabel('Y'); zlabel('Z')

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See also:

https://www.mathworks.com/help/matlab/math/delaunay-triangulation.html

Another simple example:

https://www.mathworks.com/matlabcentral/answers/1890712-using-matlab-to-generate-complex-graphics-stl-file

A more complicated case with multiple boundaries, still using the same idea:

https://www.mathworks.com/matlabcentral/answers/129269-how-to-make-a-stl-file-from-a-mesh