This graphic was created in MATLAB using the following code:

%create u-v grid space
u=linspace(0,2*pi,120);
v=linspace(0,2*pi,120);
[u,v]=meshgrid(u,v);

R=0.5;                  %set large radius of torus
r=abs(cos(v/2))*0.2;    %set small radius to vary with angle

%parametrization
x=(R+r.*cos(u)).*cos(v);
y=(R+r.*cos(u)).*sin(v);
z=r.*sin(u);

H=surf(x,y,z);
set(H,'FaceColor',[0.25 0.25 0.75],'EdgeColor','none');
set(H,'SpecularColorReflectance', 0.2, 'DiffuseStrength', 0.8);
set(H,'AmbientStrength', 0.3,'FaceLighting','phong');
set(H,'SpecularExponent', 100);

daspect([1 1 1]);   %set ratio of x,y,z axes
axis tight;         %fit axes to figure
axis off;           %don't show axes
view(190, 40);      %set viewing angle
camlight (-50, 54); lighting phong; %add light source

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