# plotting a 3d surface on the screen of an oscilloscope

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EMMANUEL VIRATEL on 31 Jan 2021
Hello everyone,
I'm Emmanuel, a student from Toulouse (France). I've found this exemple on mathworks
and it works but i want to get the coordonates in a plan 2D in order to send it to the soundcard of my computer and drawing it on my oscilloscope. I want to get the most beautiful figure. I've made a script (after the original script, it use the function viewmtx), but i'm not satisfy by the result. Pleased would you help me!!!
my email: viratelemmanuel@yahoo.fr
The original script from mathworks
theta = 0:pi/40:pi; % polar angle
phi = 0:pi/20:2*pi; % azimuth angle
[phi,theta] = meshgrid(phi,theta); % define the grid
degree = 6;
order = 1;
amplitude = 90;
radius = 5;
Ymn = legendre(degree,cos(theta(:,1)));
Ymn = Ymn(order+1,:)';
yy = Ymn;
for kk = 2: size(theta,1)
yy = [yy Ymn];
end
yy = yy.*cos(order*phi);
order = max(max(abs(yy)));
rho = radius + amplitude*yy/order;
r = rho.*sin(theta); % convert to Cartesian coordinates
x = r.*cos(phi);
y = r.*sin(phi);
z = rho.*cos(theta);
figure
s = surf(x,y,z);
light % add a light
lighting gouraud % preferred lighting for a curved surface
% axis equal off % set axis equal and remove axis
% view(40,-10) % set viewpoint
camzoom(1.5) % zoom into scene
scale = [ linspace(1,-1,40)]; % surface scaling (0 to 1 to -1)
while true
for ii = 1:length(scale)
rho = scale(ii)*amplitude;
% r = rho.*sin(theta);
% x = r.*cos(phi);
% y = r.*sin(phi);
% z = rho.*cos(theta);
%
% s.XData = x; % replace surface x values
% s.YData = y; % replace surface y values
% s.ZData = z; % replace surface z values
view(rho,rho);
pause(0.05) % pause to control animation speed
end
end
My script with viewmtx and a projection
theta = 0:pi/40:pi; % polar angle
phi = 0:pi/20:2*pi; % azimuth angle
[phi,theta] = meshgrid(phi,theta); % define the grid
degree = 6;
order = 1;
amplitude = 90;
radius = 5;
Ymn = legendre(degree,cos(theta(:,1)));
Ymn = Ymn(order+1,:)';
yy = Ymn;
for kk = 2: size(theta,1)
yy = [yy Ymn];
end
yy = yy.*cos(order*phi);
order = max(max(abs(yy)));
rho = radius + amplitude*yy/order;
r = rho.*sin(theta); % convert to Cartesian coordinates
x = r.*cos(phi);
y = r.*sin(phi);
z = rho.*cos(theta);
scale = [ linspace(1,-1,40)];
for ii = 1:length(scale)
rho = scale(ii)*amplitude;
%A = viewmtx(-37.5,30);
A = viewmtx(rho,rho);
r=x(23,:);
b=y(20,:);
c=z(20,:);
m=41;
n=1;
x4d = [r;b;c;ones(n,m )];
x2d = A*x4d;
x2 = zeros(m,n); y2 = zeros(m,n);
x2(:) = x2d(1,:);
y2(:) = x2d(2,:);
plot(x2,y2);
% ones(m*n,1)
% plot(y(:,t),z(:,t));
pause (0.5)
end
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