How to rotate or align point cloud ?

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Lyhour Chhay 2021-12-25

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评论： Lyhour Chhay 2021-12-27

Excuse me everyone! I have point cloud as shown in the figure. I want to rotate to the horizontal plane. The rotation point is the middle. How can I do it ? Thank you very much.

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Matt J 2021-12-25

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编辑：Matt J 2021-12-26

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Since your point cloud is is not perfectly coplanar, you will need to fit a plane to it in order to determine the necessary rotation. You can do that with planarFit() from this downloadable package:

https://www.mathworks.com/matlabcentral/fileexchange/87584-object-oriented-tools-for-fitting-conics-and-quadrics

pfit=planarFit(plyRoi.Location.');

Having done this, you can also use some of the Hidden methods of the pfit object to do the rotation:

XYZ=plyRoi.Location;
x0=mean(XYZ);
R=pfit.vecrot(pfit.normal,[0,0,1]); %compute 3x3 rotation matrix
result=pointCloud((XYZ-x0)*R.'+x0); %rotated point cloud

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Matt J 2021-12-26

编辑：Matt J 2021-12-26

在 MATLAB Online 中打开

Here is the code I used, and the results I obtained,

XYZ=plyRoi.Location;
pfit=planarFit(XYZ');
x0=mean(XYZ);
R=pfit.vecrot(pfit.normal,[0,0,1]); %compute 3x3 rotation matrix
result=num2cell((XYZ-x0)*R'+x0,1); %rotated point cloud
[hF,h1]=plot(pfit); hold on
h2=scatter3(result{:},'filled','MarkerFaceColor','g'); hold off
axis(0.07*[-1,1,-1,1,-1,0])
view(-25,3)
legend([h1,hF,h2],'Old Cloud','Plane Fit','New Cloud',...
                  'location','north')

Lyhour Chhay 2021-12-27

Dear Image Analyst and Matt J,

I really apprecicate your kindness and thank you very much. Please apology for my late response due to it is night time for me while you were commented. Really big thank to Matt j for your coding, now I can run it and solve it. the problem is about this statement:

pfit=planarFit(plyRoi.Location); --> this statement is request big size ram
XYZ=plyRoi.Location; pfit=planarFit(XYZ'); --> working !!!! I really suprise that it is worked.

Again, thank you all for helping me to solve this problem. Have nice day and wish you the best for coming new year.

Best Regards,

CHHAY LYHOUR

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更多回答（1 个）

Image Analyst 2021-12-25

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在 MATLAB Online 中打开

You forgot to attach your data, which would have made it easier.

TUTORIAL: How to ask a question (on Answers) and get a fast answer

So I'd guess at something like

% Fit a line through the data.
coefficients = polyfit(x, y, 1);
% Then get the mean y
meany = mean(y);
% Get a fitted y
fittedy = polyval(coefficients, x);
% Then subtract the fitted values and add the vertical offset.
rotatedy = y - fittedy + meany;
plot(x, rotatedy, '.', 'MarkerSize', 10);

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Image Analyst 2021-12-25

Well give him time - it is Christmas Day after all. 🎅

Lyhour Chhay 2021-12-26

Dear Sir (Image Analyst)

Thank you very much sir for your suggestion and guidance. I am sorry for my late response due to different time zone. Merry Christmas wish you the best. Thank you sir.

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