Rolve function around axis to create 3D surface.

Hello,

I am fairly new to matlab and know the basics. I am trying to create a 3D surface from the function y by revolving it around the x axis. The function is the profile of the tip of a bullet and I am looking to obtain a 3D plot. Thank you in advance!

x = linspace(0,1,100);
y = (2).*(x./12).^0.5;

Answer 1

[Star Strider]

See: Plotting an exponential exp(-x), in 3D? for an example.

[MLP]

Hi! thank you for forwarding me to the answer. Although I seem to have an issue, the axis of rotation is at the other extreme of the function and I do not know how to specify the lenght. Here I attached a sketch of what I am looking for in hopes you can help me. I couldn't attach an image for the resultant figure.

figure(); hold on;
for theta = linspace(0, 2*pi, 50) % Not exactly sure how you want to vary theta
    [T, R] = meshgrid(linspace(0, theta, 50), linspace(0,2,50));
    [X, Y] = pol2cart(T,R); 
    Z = (2).*(R./12).^0.5; % Compute the surface of revolution
    surf(X,Y,Z); % Plot the surface
    pause(1); % Wait one second
end

[Star Strider]

I managed to get it to work.

The Code —

a = linspace(0, 2*pi, numel(r));
r = linspace(0,1,100);
[A,R] = ndgrid(a,r);
Z = (2*sqrt((R)/12));                                       % Calculate Curve

[X,Y,Z] = pol2cart(A,Z,R);                                  % Set ‘Z’ As The Radius Matrix, ‘R’ Matrix As ‘Z’

figure
mesh(Z, Y, X, 'FaceAlpha',0.75)
grid on
axis('equal')                                               % Avoid Scaling Distortion
hold on
plot3(xlim+[-0.1 0.1], [0 0], [0 0], 'k', 'LineWidth',2)    % Centre Axis (If Needed)
hold off

The Plot —

I added a centre axis line just for fun, and set 'FaceAlpha' at less than 1 to make it visible. You can eliminate it by simply eliminating everything after the axis call.

Experiment to get different results.

This was a bit of a challenge!

[MLP]

hey thank you so much for taking the time to help me out, it works perfectly!

[Star Strider]

As always, my pleasure!

Answer 2

[Gurpreet Singh]

Hi Mateo,

It is my understanding that you are trying to create a 3D surface using a 2D plot by revolving it around the x axis.

The following links might help you.

https://stackoverflow.com/questions/22031279/matlab-2d-plot-parabolic-line-rotation-to-form-a-cone-in-3d

https://in.mathworks.com/matlabcentral/answers/349969-3d-rotation-matrix