MATLAB: How to make irregular 3d shape with spherical coordinates

meshsurfsurface

Hi, I have some different values of 'r' in spherical coordinates and want to plot 3d irregular surface. e.g, I have phi = [0,2pi] and theta = [0,pi/2], so for each phi and theta, I have different r value. I just want to plot the surface, with no color, and only showing the variation in r by 3d surface.

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Attaching a sample code. I have converted the spherical coordinates to Cartesian, keeping radius variable as a vector. Further I have used surf function for the 3d plot.

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MATLAB: How to find volume under fitted data

If you have a function y = f(r), which it sounds like you do since you have a polynomial, then you can use integral.

y = @(r) 1-r; % y can be any arbitrary function of r. Put the function for your curve here (POLYVAL?).
a = 0; % Some limits of integration r = a to b
b = 1;
% Volume under surface of rotation:
vol = 2*pi*integral(@(r) y(r) .* r, a, b) % Put in the extra  ".*r" for polar coords.

Here I used y = 1-r, so it is a cone, and I can verify that the answer I got (vol=1.047) was indeed equal to the analytical answer for the volume of a cone with unit height and radius (pi/3).

If you don't have a function, but just some discrete set of values r and y, then you can use INTERP1 along with INTEGRAL.

r = [ 0 0.2 0.4 0.6 0.8 1.0 ]; % Again, just use a unit cone for testing purposes
y = [ 1 0.8 0.6 0.4 0.2 0   ];
Yfun = @(p) interp1(r, y, p); 
vol = 2*pi*integral(@(r) Yfun(r).*r, 0, 1) % Again, you'll get 1.0472

MATLAB: Display a 3D image with texture

Try using TriScatteredInterp() to make a solid surface where you have a z for every x and y pairing. Then use surf() or imshow() to plot the complete surface.

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MATLAB: How to find volume under fitted data

MATLAB: Display a 3D image with texture

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