Create mesh from matrix

I have two matrix a and b, which have dimension of 241 x 360. The values from the a and b gives a mesh. How do I plot the mesh?

[Walter Roberson]

Could you give an example of what you are hoping the output might look like?

[Kiran]

For example, lets assume a and b are 2x2 matrix. where the elemnts values are,

a(1,1) = 0, a(1,2) = 2 , a(2,1) = 0, a(2,2) = 2

b(1,1) = 0, b(1,2) = 23 , b(2,1) = 50, b(2,2) = 50

This represents the four corner of a quadrilateral, with respective combination of indices. Like, a(1,1) and b(1,1) first corner and so on.

[the cyclist]

OK, so for your small example, what would the output actually be? Don't worry how to calculate it. Just tell us the output result.

a = [0 2;
     0 2];

b = [ 0 23;
     50 50];

ab_mesh = ????

[Walter Roberson]

Are you trying to create a solid? Where the bottom is given by one of the matrices and the top is given by the other matrix, and they are assumed to be some set distance apart? If so then how do you want to handle the situation where they have different number of vertices?

[Kiran]

The output on matlab should look like this. A grid formed using martix a and b.

[Walter Roberson]

@Kiran

But you asked for a mesh, and what you show is not a mesh.

[Kiran]

Yes, but that's just for example the real matrix has dimension 241 x 55298 for a and b, so lot of points to form grid. My question was, can we get a grid in matlab if we know the elements of a and b?

[Image Analyst]

@Kiran did you even see my answer from yesterday below (scroll down)?

Answer 1

[Walter Roberson]

a = [0 2 3;
     0 2 4];
b = [ 0 2.3 4;
     5 5 3];

h = size(a,1);
w = size(a,2);
idx = reshape(sub2ind([h, w], 1:h*w), h, w);

tl = idx(1:end-1, 1:end-1);
tr = idx(1:end-1, 2:end);
ll = idx(2:end, 1:end-1);
lr = idx(2:end, 2:end);
T = [tl(:), ll(:), lr(:), tr(:)];
X = [a(:), b(:), zeros(numel(a),1)];
tetramesh(T, X)
view(2)

[Walter Roberson]

The sub2ind() is not needed...

a = [0 2 3;
     0 2 4];
b = [ 0 2.3 4;
     5 5 3];

h = size(a,1);
w = size(a,2);
idx = reshape(1:h*w, h, w);

tl = idx(1:end-1, 1:end-1);
tr = idx(1:end-1, 2:end);
ll = idx(2:end, 1:end-1);
lr = idx(2:end, 2:end);
T = [tl(:), ll(:), lr(:), tr(:)];
X = [a(:), b(:), zeros(numel(a),1)];
tetramesh(T, X)
view(2)

Answer 2

[Image Analyst]

Not sure what you mean by "plot" but to view a and b as 2-D images and 2.5-D surface plots:

subplot(2, 2, 1);
imshow(a, []);
subplot(2, 2, 2);
imshow(b, []);
subplot(2, 2, 3);
surf(a);
subplot(2, 2, 4);
surf(b);

Or you could simply double click on a and b in the workspace panel to bring them up in the variable editor panel in MATLAB.

[Kiran]

I got something like this. But, can you let me know hwo to get a 2d plot, like in the sketch?