Here is a new figure I made today in honor of Tom's 65th birthday. Guessing the function(s) should be fairly easy for him...
I've appended the code I used to generate it.
height=3.0; strandwidth=1; nstrands=20; tuberad=(1./nstrands).*6; [U,V]=meshgrid(0:0.2:2.*pi+.2,0:.1:height.*pi+.1); Z=tuberad.*sin(U)+V.*3; hold on; for ct=1:nstrands X=(ct+2+strandwidth.*cos(U)).*tuberad.*cos(V+2.*(ct1).*pi./nstrands); Y=(ct+2+strandwidth.*cos(U)).*tuberad.*sin(V+2.*(ct1).*pi./nstrands); Col=V; s1=surf(X,Y,Z,Col); end

