# Problem with while loop

2 views (last 30 days)
Kevin Hanekom on 13 Apr 2021
Commented: Kevin Hanekom on 13 Apr 2021
Hello,
The goal of my code is to plot the function for a Tsai-Wu surface which is supposed to be a ellipsoide, the problem arrises with my while loop which does not seem to be doing anything. I've simplified the equation, but as you can see the value for my variable G can never excede 1. Any help or a pointer in the right direction would be really appreciated, thanks!
sig1c = -1.5; %always set compression as negative
sig1t = 1; %always set tension as positve
sig2c = -1.5;
sig2t = 1;
sig3c = -2;
sig3t = 0.5;
F1 = ((1/sig1t)-(1/sig1c));
F2 = ((1/sig2t)-(1/sig2c));
F3 = ((1/sig3t)-(1/sig3c));
F11 = (1/(sig1c*sig1t));
F22 = (1/(sig2c*sig2t));
F33 = (1/(sig3c*sig3t));
syms sig1 sig2 sig3 G
% sig1 = 0;
% sig2 = 0;
% sig3 = 0;
%[sig1,sig2,sig3] = meshgrid(linspace(-5,5,25));
%G = F1.*sig1 + F11.*sig1.^2 + F2*sig2 + F22.*sig2.^2 + F3.*sig3 + F33.*sig3.^2 - 1;
[sig1,sig2,sig3] = meshgrid(linspace(-5,5,25));
while G < 1
G = F1.*sig1 + F11.*sig1.^2 + F2*sig2 + F22.*sig2.^2 + F3.*sig3 + F33.*sig3.^2 - 1;
end
fv = isosurface(sig1,sig2,sig3,G,0);
fv = isosurface(G,0);
fvc = isosurface(G,'red');
p = patch(isosurface(sig1,sig2,sig3,G,0));
%isonormals(sig1,sig2,sig3,G,p)
%isonormals(sig1,sig2,sig3,G,p)
view(3);
##### 2 CommentsShowHide 1 older comment
Kevin Hanekom on 13 Apr 2021
Im new to programing so alot of this is blury to me but the goal is to use different values of sig1, sig2, and sig3, up to a point where g is <=1, and then plot those points forming a ellipsoid

Chunru on 13 Apr 2021
Change
while G < 1
G = F1.*sig1 + F11.*sig1.^2 + F2*sig2 + F22.*sig2.^2 + F3.*sig3 + F33.*sig3.^2 - 1;
end
to:
G = F1.*sig1 + F11.*sig1.^2 + F2*sig2 + F22.*sig2.^2 + F3.*sig3 + F33.*sig3.^2 - 1;
Kevin Hanekom on 13 Apr 2021
Great thank you for helping me! You guys are what make this community so great.

R2021a

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