MATLAB: How to plot a cute sphere

ovoidsphere

hi. i tried to plot a sphere with sphere function. but the sphere was very ugly. and it was more like an ovoid. plz help me to plot a nice sphere. something like this pic

a=[0 0 0];
[e,f,g] = sphere(30);
e=e*0.3;
f=f*0.3;
g=g*0.3;
s1=surf(e+a(1),f+a(2),g+a(3),'FaceAlpha',0.2,'FaceColor','r')

Best Answer

If you don't have access to the cuteSphere toolbox, you can just use this line of code below to make the sphere appear as a sphere.

%[your plotting code] 
axis equal

The reason your sphere appeared as an ovoid is because the data aspect ratio is not equal.

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MATLAB: Plot a marker in the center of the circle

Add this after the fill call:

plot(x, y, 'kp', 'MarkerSize',15, 'MarkerFaceColor','k')

Also consider separate arguments for the marker colour and size.

MATLAB: Plot spheres in 3D with one color (no gradient)

A solid FaceColor alone isn't going to give you any feeling of the 3D shape of the spheres. If you take the edges away, you'll need to use something else to show the shape.

One option is lighting:

N = 15;
a = 1/8;
XT = randn(1,N)/6;
YT = randn(1,N)/6;
ZT = randn(1,N)/6;
for j=1:N
  % Generate a sphere consisting of 20by 20 faces
  [x,y,z]=sphere;
  % use surf function to plot

  hSurface=surf(a*x+XT(j),a*y+YT(j),a*z+ZT(j));
  hold on
  set(hSurface,'FaceColor',[0 0 1], ...
      'FaceAlpha',0.5,'FaceLighting','gouraud','EdgeColor','none')
  axis([-0.5 0.5 -0.5 0.5 -0.5 0.5]);
  daspect([1 1 1]);
end
hold off
xlabel('X')
ylabel('Y')
zlabel('Z')
camlight

Another option would be to use FaceColor to shade them:

N = 15;
a = 1/8;
 XT = randn(1,N)/6;
YT = randn(1,N)/6;
ZT = randn(1,N)/6;
[x,y,z]=sphere;
l = [.25 -.433 .5];
c = max(0,x*l(1) + y*l(2) + z*l(3));
for j=1:N
  % use surf function to plot
  hSurface=surf(a*x+XT(j),a*y+YT(j),a*z+ZT(j),c);
  hold on
  set(hSurface,'FaceColor','interp','FaceAlpha',0.5,'EdgeColor','none')
  axis([-0.5 0.5 -0.5 0.5 -0.5 0.5]);
  daspect([1 1 1]);
end
hold off
xlabel('X')
ylabel('Y')
zlabel('Z')
colormap hot

Best Answer

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MATLAB: Plot a marker in the center of the circle

MATLAB: Plot spheres in 3D with one color (no gradient)

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