This math image could be re-created using vector graphics as an SVG file. This has several advantages; see Commons:Media for cleanup for more information. If an SVG form of this image is available, please upload it and afterwards replace this template with {{vector version available|new image name}}. It is recommended to name the SVG file “TorusSystoleLoop.svg”—then the template Vector version available (or Vva) does not need the new image name parameter.

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+0.05;   %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);
hold on;			    %put a hold on this figure
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

%add another torus to show tightest place on the torus
R2=0.075;
r2=0.025;

x2=(R2+r2.*cos(u)).*cos(v)-0.5;
y2=r2.*sin(u);
z2=(R2+r2.*cos(u)).*sin(v);

H2=surf(x2,y2,z2);
set(H2,'FaceColor',[0.75 0.25 0.25],'EdgeColor','none');
set(H2,'SpecularColorReflectance', 0.2, 'DiffuseStrength', 0.8);
set(H2,'AmbientStrength', 0.5,'FaceLighting','phong');
set(H2,'SpecularExponent', 100);

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