3D plot an ellipsoid?

hi, i'm making a code that will plot an ellipsoid with the following equations:

x = a * (cos*phi) * (cos * theta); y = b * (cos*phi) * (sin * theta); z = b * (sin*phi);

and i'm supposed to plot it with a = 2, and b = 1, but it doesn't appear to be working.. help anyone?

a = 2;
b = 1;

x = a * (cos*phi) * (cos * theta);
y = b * (cos*phi) * (sin * theta);
z = b * (sin*phi);

[Xm, Ym] = meshgrid(x,y);

surf(x,y,z)

[Rik]

phi and theta don't exist and you are using them as input to cos and sin.

Answer 1

[Akira Agata]

How about using a fsurf function, like:

a = 2;
b = 1;

funx = @(theta,phi) a*cos(theta).*cos(phi);
funy = @(theta,phi) b*cos(theta).*sin(phi);
funz = @(theta,phi) b*sin(theta);

fsurf(funx,funy,funz,[-pi/2 pi/2 -pi pi])

[Mat Ramada]

wow, that fixed it! thank you so much!

[Ahmed Karoui]

Hi,

I´m wondering how I can transform (Rotate) this ellipsoid having already a rotation-matrix for example.

How can I execute the Rotation with the Matrice that I have if I defined my ellipsoid using function handles ?

[Akira Agata]

How about using hgtransform ? The following is an example.

a = 2;
b = 1;
funx = @(theta,phi) a*cos(theta).*cos(phi);
funy = @(theta,phi) b*cos(theta).*sin(phi);
funz = @(theta,phi) b*sin(theta);

% Make rotation matrix (e.g Rotate pi/4 [rad] for y-axis)
M = makehgtform('yrotate',pi/4);

figure
h = fsurf(funx,funy,funz,[-pi/2 pi/2 -pi pi]);
daspect([1 1 1])

% Apply the rotation matrix
t = hgtransform('Parent',gca);
t.Matrix = M;
h.Parent = t;

[DOMENICO GIOFFRE]

Hello. I have a 3x3 matrix describing a tilted ellypsoid. How can i plot this? Besides, is there a way to calculate the distance between its center and a point on the surface in the direction of x, y and z axes?

Thank you!

229.435 1.889 -5.708

1.889 207.544 4.372

-5.708 4.372 184.297

how can I rotate it 'back'