# sphere made of 2d circles in 3d plot

6 views (last 30 days)
reza on 2 Jan 2014
Edited: Roger Stafford on 2 Jan 2014
hi i made the code below the create a sphere using 2d circles in a 3d plot:
r=1
teta=-pi:0.01:pi
x=r*cos(teta);
y=r*sin(teta);
axis square
for i=0.0:0.1:1
z=i*sin(teta);
plot3(x,y,z);
hold on
end
for i=0.0:-0.1:-1
z=i*sin(teta);
plot3(x,y,z);
hold on
end
for i=0.0:0.1:1
y=i*sin(teta);
plot3(x,y,z);
hold on
end
for i=0.0:-0.1:-1
y=i*sin(teta);
plot3(x,y,z);
hold on
end
however it doesn't create a clear sphere from some views it shows sphere from some views it shows something( i don't know what ).
anyway i want to creat a sphere using the code below to create a sphere using 2d circles(code below).
r=1
teta=-pi:0.01:pi
x=r*cos(teta);
y=r*sin(teta);
z=zeros(1,numel(x));
plot3(x,y,z);
Walter Roberson on 2 Jan 2014

Amit on 2 Jan 2014
You can use sphere function to create a sphere. Do you specifically need sphere from circles?
Amit on 2 Jan 2014
Moreover, the equation you have used does not represent a sphere.
Amit on 2 Jan 2014
If you really just want to use 2-D circles, the code will be something like this:
r=1;
teta=-pi:0.1:pi;
x=zeros(size(teta));
y=x;
z = x;
axis square
for i=(-1)*r:0.1:r
x = ((r^2-i^2)^0.5)*cos(teta);
y = ((r^2-i^2)^0.5)*sin(teta);
z = i*ones(size(teta));
plot3(x,y,z);
hold on;
end

Roger Stafford on 2 Jan 2014
Edited: Roger Stafford on 2 Jan 2014
To use 'surf' do this:
r = 1;
[theta,phi] = ndgrid(linspace(0,pi),linspace(0,2*pi));
X = r*cos(phi).*sin(theta);
Y = r*sin(phi).*sin(theta);
Z = r*cos(theta);
surf(X,Y,Z)
or if you just want circles, do this:
r = 1;
[theta,phi] = ndgrid(linspace(0,pi),linspace(0,2*pi));
X = r*cos(phi).*sin(theta);
Y = r*sin(phi).*sin(theta);
Z = r*cos(theta);
for k = 1:numel(theta)
plot3(X(k,:),Y(k,:),Z(k,:))
hold on
end
(Corrected)