How to turn 3D surface into STL file with surface?

The attached MATLAB code produces a 3D surface. How can I give the surface some thickness and export it as an STL file?

% Data points forming a figure eight in 3D space

x = [-54 -58 -47 -43 -54 -65 -61 -50 -54];

y = [ 20 32 38 26 20 13 1 7 20];

z = [ 82 76 82 88 82 76 82 88 82];

% Plot the data points and write their serial numbers

n = length(x);

plot3(x,y,z,'r-*'), axis equal

hold on

for i = 1:n, text(x(i),y(i),z(i),num2str(i)), end

% Create and plot a periodic spline (space curve) through the data points

n = length(x);

t = 0:n-1;

ppx = csape(t,x,'periodic');

ppy = csape(t,y,'periodic');

ppz = csape(t,z,'periodic');

fxc = @(t) fnval(ppx,t);

fyc = @(t) fnval(ppy,t);

fzc = @(t) fnval(ppz,t);

fplot3(fxc,fyc,fzc,[0 n-1],'b','LineWidth',3)

% Create and plot a parametric surface based on the spline

fxs = @(s,t) s.*fxc(t);

fys = @(s,t) s.*fyc(t);

fzs = @(s,t) s.*fzc(t);

fsurf(fxs,fys,fzs,[0 1 0 n-1])

legend('Data points','Space curve (spline)','Surface')

Answer 1

[Henning Søgaard]

I solved the problem myself by adding the following code:

% Give surface some thickness and convert to stl-file

% (The solid surface is built from the space curve)

% (surf2solid was downloaded from https://se.mathworks.com/matlabcentral/fileexchange/30709-surf2solid)

t = (0:1/4:n-1)';

X = [0; fxc(t)]; % X-coordinates: zero and space curve x-coords.

Y = [0; fyc(t)]; % Y-coordinates: zero and space curve y-coords.

Z = [0; fzc(t)]; % Z-coordinates: zero and space curve z-coords.

V = [X Y Z]; % Vertices for surface triangles

n = height(V);

F = [ones(n-2,1) (2:n-1)' (3:n)']; % Triangle faces (row indices within V)

FV.faces = F; FV.vertices = V;

[F,V] = surf2solid(FV,'thickness',1); axis image; camlight;

tr = triangulation(F,V);

stlwrite(tr,'temp.stl');