How t generate cone using scattered random point cloud?
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Using the below code, i have geneated sphere. could anyone please guide me how to geneate cone using random scattered point cloud.
I will be very thankful. Thanks in advance to all community members for their cooperation and guidance. Regards
r = randn (10000,3);
r = round(bsxfun(@rdivide,r,sqrt(sum(r.^2,2)))*130);
x = r(:,1);
y = r(:,2);
z = r(:,3);
scatter3(x,y,z)
采纳的回答
Bruno Luong
2020-10-20
编辑：Bruno Luong
2020-10-20
This code provides the uniform distribution on the surface of the cone
h = 3; % height
r = 1; % base radius
n = 1e4; % number of points
topcapflag = true; % include the top cap or not
rho = sqrt(rand(1,n));
z = h*rho;
if topcapflag
z(rand(1,n)<r/(h+r))=h;
end
theta = (2*pi)*rand(1,n);
rho = r*rho;
x = cos(theta).*rho;
y = sin(theta).*rho;
% graphic check
figure
plot3(x,y,z,'.')
axis equal
更多回答（1 个）
Ameer Hamza
2020-10-20
This is one way. The distribution is non-uniform
h = 2; % height of cone
r = 1; % maximum radius of cross section of the cone
n = 10000;
z = rand(1, n)*h;
t = rand(1, n)*2*pi;
r = interp1([0 h], [0 r], z);
[x, y] = pol2cart(t, r);
scatter3(x, y, z)
23 个评论
M.S. Khan
2020-10-20
Ameer Hamza
2020-10-20
First, it generates z coordinates and then, based on z value, calculates x and y coordinates that line on the circle.
M.S. Khan
2020-10-21
M.S. Khan
2020-10-21
Ameer Hamza
2020-10-21
interp1() is a 1D interpolation. This line map value in range 0 to h, to the range 0 to r.
M.S. Khan
2020-10-21
Ameer Hamza
2020-10-21
Yes, rand gives uniformly distributed z coordinates. So you get an almost equal number of points for all values of z. But the circumference at the difference value of z is not the same. So at the bottom, the points are densely packed, but at the top, they have a lesser density.
M.S. Khan
2020-10-21
Ameer Hamza
2020-10-21
You can use writematrix() to write to a .txt file.
M.S. Khan
2020-10-21
Ameer Hamza
2020-10-21
No, the correct syntax is
writematrix([x(:) y(:) z(:)], 'M.txt')
M.S. Khan
2020-10-21
Ameer Hamza
2020-10-21
I am glad to be of help!
M.S. Khan
2020-10-21
M.S. Khan
2021-3-4
anuradha verma
2022-11-7
hello sir, can you please help me how to generate unformly distributed points inside a cone.
@anuradha verma This code generates uniform data inside the volume of the half cone with axis parallel to z axis
Rmax = 1; % cone base radius
Zmax = 2; % cone height
N = 1e4; % Number of point
z = rand(1,N).^(1/3);
r = Rmax*sqrt(rand(1,N)).*z;
theta = (2*pi)*rand(1,N);
x = r.*cos(theta);
y = r.*sin(theta);
z = Zmax*z;
scatter3(x,y,z);
axis equal
anuradha verma
2022-11-10
anuradha verma
2022-11-10
Sir can you help me with the algorithm for the generation of uniformly distributed points inside the volume of a frustrum. Thanks a lot for your help.
Bruno Luong
2022-11-10
Please open new question and ideally stop hacking other people's question for cohesion.
anuradha verma
2022-11-10
Sir I am sorry if i have done anything wrong. I am new to matlab so i don't know much about it. Kindly forgive me.
Bruno Luong
2022-11-10
编辑：Bruno Luong
2022-11-10
@anuradha verma, it's not difficult, if you have new question, just click on Ask, or this link:https://mathworks.com/matlabcentral/answers/questions/new
then describe the problem accurately,.
This thread is opened by the author for his problem and it's has been answered.
You question merits a new thread
anuradha verma
2022-11-11
Thank you sir.
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