Levelling of 3D built in stl file

Hello Community,

I have a stl file of 3D image. This image is titled 45 degree. I want to level (project) it on a plane so that I could get z values (height of the different parts of the cracks). For details please have a look at the attachment. This is sample which contains many cracks. Some of the cracked are elevated, i.e., curled ups. I want to know the height of these curlings. Thanks.

[darova]

You forgot to attach the image :(

[Noor Mohammad]

It is uploaded now. Thanks drova for your response.

Answer 1

[KSSV]

Download this file exchange function:

https://in.mathworks.com/matlabcentral/fileexchange/22409-stl-file-reader

[t,p] = stlread('Tr_3.stl') ;
% Rotate along z axes by 45 degrees
th = 45 ; 
R = [cosd(th) -sind(th) 0 ; sind(th) cosd(th) 0 ; 0 0 1] ;   % Rotation matrix 
pr = p*R ;   % Rotate the points 
pr(:,3) = pr(:,3)-mean(pr(:,3)) ; 
% plot 
trisurf(t,pr(:,1),pr(:,2),pr(:,3),'EdgeColor','none')

xlabel('x')
ylabel('y')
zlabel('z')

[Noor Mohammad]

Dear KSSV,

Thank you so much for your answer. I think you solution gives the view that looks like parallel to z-axis. However, I want to do levelling of the image so that I can find the elevation based on a datum and can compare the heights of the cracked surfaces following that datum. Please help if possible. Thanks again.

Regards,

Noor

[KSSV]

How you want to do levelling? What do you mean by that?

[Noor Mohammad]

Actually, I want to something like this attachment. I want to measure the height of the curling cracks using the z-values obtained from matlab. I think it would be clear now. Thank you so much for your efforts..

[KSSV]

Okay.....the points have been shifted to (x,y) plane and mean is removed along z......wont this work out?

[DGM]

I'm going to assume that the datum is the lowest point, since the material can't intersect with the container.

% for the forum
unzip Tr_3.zip

% Inputs
T = stlread('Tr_3.stl'); % built-in since R2018b
th = -45; % parameter

% Since we're using the built-in reader
F = T.ConnectivityList;
V = T.Points;

R = [1 0 0; 0 cosd(th) -sind(th); 0 sind(th) cosd(th)]; % Rotation matrix 
Vr = V*R; % Rotate the points around x
Vr(:,3) = Vr(:,3) - min(Vr(:,3)); % Remove z-offset

% Plot 
trisurf(F,Vr(:,1),Vr(:,2),Vr(:,3),'EdgeColor','none')
xlabel('x')
ylabel('y')
zlabel('z')
axis equal

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