Geometric Analysis of cross-seciton

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Devrim Tugberk 2019-7-23

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评论： darova 2019-7-29

Dear Matlab Community,

I have a 3D scatter plot representing a cross-section of a vessel. My goal is to have a script that will: identify the center of this cross-section and generate lines from this centerpoint in a circular motion in increments of 1 degrees between each line (up to 360 degrees).

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darova 2019-7-23

What have you done already? Do you have any ideas?

Devrim Tugberk 2019-7-25

I didn't achieve much yet. My communication with the program still is very limited. The only thing i achieved was to locate the centerpoint for each cross-section (without a script).

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darova 2019-7-25

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Simple formula of polygon centroid: WIKI

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Devrim Tugberk 2019-7-26

在 MATLAB Online 中打开

cross_secitions.mat

I have another script that extracts this cross_sections data (not relevant) and the script below extracts the cross_sections data from each cell and plots them:

vv=cellfun(@(x) x(:,1:3),Cross_sections,'un',0); % assuming the first three columns in each cell represents x,y & z
v=cat(1,vv{:}); % gathering x,y, & z of each cell into one matrix
scatter3(v(:,1),v(:,2),v(:,3))
%         ^- x    ^- y   ^- z
axis equal % equal axis lengths
for k = 1:size(vv) %numel
figure(k);
scatter3(vv{k}(:,1),vv{k}(:,2),vv{k}(:,3));
end

and here is the script you provided regarding the lines which is what i want:

t = 0:5:360;
r = 2; 
x0 = 199;
y0 = 29;
x = r*cosd(t) + x0;
y = r*sind(t) + y0;
hold on
for i = 1:length(x)
    plot([x0 x(i)],[y0 y(i)],'.-r')
end
hold off

The last few things i need are:

1) the addition of z since we are working 3D

2) i need these lines generated for each, individual cross_section automatically on the same plot

3) x0 and y0 need to be the centroid of each cross_section and should be re-calculated for each cross_section individually.

Again, thank you so much for working me through this

Devrim Tugberk 2019-7-29

编辑：Devrim Tugberk 2019-7-29

no problem!

So i need the coordinate data corresponding to the green dots (all of the points, not just the ones i drew) that i have drawn on the image. The green dot representing the intersection between the blue lines and the red lines.

Thank you