How can I create a 3D solid body from a surface plot (x y z data points) and export it (preferably as STL) to a CAD software?

I have an x y z dataset and I want to create a solid 3D body (almost as if 'extruding' the surface down in a CAD software) from the topmost 3D surface. I am trying to achieve something similar to this

.

Having tried that, I am getting the following error :

Error using stlwrite (line 25)

Input argument must be a triangulation object.

Error in surface_to_3D (line 22)

stlwrite('test3D.stl',test3D);

If anyone could help me solve this, or tell me an alternative way to achieve this, that would be very helpful. All required files that I have used are attached.

P.S. The reason I cannot do it in a CAD software is because Solidworks or any other software cannot really read/detect the surface for extrusion, even if I use surf2stl to export it as an STL file.

Answer 1

[Walter Roberson]

There are file exchange contributions for surf2stl() and patch2stil()

[SNIreaPER]

The code that I have enclosed in the zipped folder uses surf2stl itself, but it just generates an stl file of the surface (brown image). What I want is to fill the region underneath and make it a solid 3D (red and green image), to be ultimately able to use it as an input for FEM.

[Bruno Luong]

But you wrote "3D solid surface" in the subject.

[SNIreaPER]

My bad - I edited the subject and question; thanks for bringing it to my attention.