Reconstructing a surface from mesh points and function values (from COMSOL)
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After having gotten more to grips with MATLAB/COMSOL LiveLink, I think I have found how to extract the mesh vertex coordinates and values of the dependent variable at those points.
I have stored these in the variables x, y, and z.
When I run plot3(x,y,z) I get the following (note that x and y are from a triangular mesh and not a rectangular grid):
I then run the following code:
x = x'; y = y'; z = z'; % Making sure these are column vectors
F = scatteredInterpolant(x,y,z);
[X,Y] = meshgrid(x,y);
Z = F(X,Y);
This seems to be a common way of constructing a surface plot from vectors that I have found online.
However, the surface plot I get looks awful:
This is the plot that the COMSOL GUI provides.
Does anyone know how I can fix it so that the surface plot produced by MATLAB (a) is much smoother, and (b) doesn't leave jagged edges at the boundary of the domain?
Bjorn Gustavsson on 9 Nov 2022
Are you sure that you need to use scatteredInterpolant at all? The points in the first plot seem to be on a regular grid. If that is the case then you're already done. If they are on a regular grid but given in some obscure ordering, you should be able to sort them into a correct order, hopefully using reshape and permute.
If your x and y are 2-D arrays you can check that things are OK byt looking at them:
x = x'; y = y'; z = z';
x = reshape(x,[14 14]);
y = reshape(y,[14 14]);
z = reshape(z,[14 14]);
It is definitely your call to meshgrid with repeated values in x and y that generates peculiarly ordered X or Y. Test this snippet just after your meshgrid call.