How to create a mesh surface from given 3D coordinates?

Hi all,

I've decided to give MATLAB a try for my research project.

I'm trying to create a 3D mesh of given coordinates E, N and elevation.

I can plot all the points using plot3(x,y,z,'.');

Using an XLSX or csv spreadsheet for the datsets I have removed all unnecessary data such as point name and code leaving only E,N and elevation in a 460x3 table.

And using the patch function it does something but not creating the surface as I would like it as a mesh.

I would also like to set some parameters when creating the mesh i.e don't create surface between outside points where distance between those points is greater than say 20m.

Attached is a screenshot of where I am up to.

Kind regards,

Mitch.

[Tommy]

Have a look at https://www.mathworks.com/matlabcentral/answers/62964-creating-3d-mesh-for-some-points-in-space

Perhaps this gives what you are looking for?

figure
tri = delaunay(x, y);
trimesh(tri, x, y, z);
hold on; plot3(x,y,z,'.')

[Mitchell Ireland]

Thanks Tommy,

That is helpful and creating the surface as i was hoping.

From here I would like to clip out the log triangles on the edges that are say over 20m between points. See red lines drawing on the screenshot below. These would roughly be the triangles to remove. Any idea if i can add this into the function or in the constraints?

Answer 1

[KSSV]

Two options:

%%structured 
xi = unique(x) ; yi = unique(y) ;
[X,Y] = meshgrid(xi,yi) ;
Z = reshape(z,size(X)) ;
figure
surf(X,Y,Z)

%%unstructured 
dt = delaunayTriangulation(x,y) ;
tri = dt.ConnectivityList ;
figure
trisurf(tri,x,y,z)

[Mitchell Ireland]

Thanks KSSV,

That is helpful and creating the surface as i was hoping with added shading that is useful in visualisation.

I could not make the structured function work?

From here I would like to clip out the long triangles on the edges that are say over 20m between points. See red lines drawing on the screenshot below. These would roughly be the triangles to remove. Any idea if i can add this into the function or in the constraints?

[KSSV]

You need to get the boundary nodes and arrange them in an order and use as constraints. Read about delaunayTraingulation. You have option of specifying constraints.

Answer 2

[Trang Cao]

Probably you don't need the answer for this anymore but I was just looking for the answer to a similar question, i.e., delaurayTriangulation do not behave well on non-convex shape.

I found alphaShape and then alphaTriangulation.

Hope this may help someone else...

Answer 3

[Dania Ahmed]

Here you need a 3D constrained delaunay to plot the domain with internal nodes in 3D. MATLAB allows constrained delaunay in 2D only.

If you wanted to plot the boudndary surface; you can use the function "boundary" with a shrink factor of 1 then trisurf the boundary and the points, i.e.

k = boundary(x,y,z,1);

trisurf(k,x,y,z,'Facecolor','red','FaceAlpha',0.5);