Building cylinder using isosurface

Hello everyone,

I'm trying to create a cylindric patch using the isosurface command. Using this tutorial I created my own structure. The code is the following:

[x,y,z] = meshgrid(-1:.02:1);
blob = z <= 0 & z >= -1 & x.^2 + y.^2 <= sqrt(0.18) & x.^2 + y.^2 >= sqrt(0.15);

p = patch(isosurface(blob,0.5));
set(p, 'FaceColor', 'red', 'EdgeColor', 'none');
view(3)
camlight
alpha(0.3)
lighting gouraud

Now, I want to specify for every level of the cylinder a different radius. The values of the radii for every level are stored in a vector 1x36.

How can I modify the blob accordingly?

Thanks for any suggestions.

Answer 1

[Matz Johansson Bergström]

I would try using a function

test = @(x) abs( cos(4*x) );

[x,y,z] = meshgrid(-1:.02:1);
blob = z <= 0 & z >= -1 & x.^2 + y.^2 <= ...
    sqrt(0.18*test(z)) & x.^2 + y.^2 >= ...
    sqrt(0.12*test(z));

In this way you will get a wobbly thing depending on the z coordinate.

[Vittorio]

Good solution, but the radius is not changing accordingly to a function. The vector which is storing the radii values is:

r=  0.8833
    0.9992
    0.9920
    0.8994
    0.9213
    0.9256
    0.9311
    0.9688
    0.9909
    0.9581
    0.9924
    0.9662
    0.8900
    0.9727
    0.9975
    0.9872
    0.9791
    1.0000
    0.9717
    0.9591
    0.9762
    0.9823
    0.9599
    0.9682
    0.9459
    0.9369
    0.9260
    0.8894
    0.9451
    0.9615
    0.9598
    0.9837
    0.9804
    0.9739
    0.9734
    0.9735

[Vittorio]

I did it! :)

Probably not an elegant solution, but here is the code:

i = 1;

[x,y,z] = meshgrid(-1:.02:1);
r1 = zeros(length(z),length(z),length(z));
step = round(length(z)/length(r));

for j = 1:step:length(z)
    r1(:,:,j) = r(i);
    if j+1>length(z)
        break
    end
    r1(:,:,j+1) = r(i);
    if j+2>length(z)
        break
    end
    r1(:,:,j+2) = r(i);
    if i>length(r)
        break
    end
    i = i+1;
end
blob = z <= 0 & z >= -1 & x.^2 + y.^2 <= sqrt(0.18*r1) & x.^2 + y.^2 >= ...
    sqrt(0.12*r1);

p = patch(isosurface(blob,0.5));
set(p, 'FaceColor', 'red', 'EdgeColor', 'none');
view(3)
camlight
alpha(0.3)
lighting gouraud

Thanks for your tip!