MATLAB: Line orientation in 3D from centroid and Euler angles

image processingMATLAB

I used the regionprops3 function to detect centroid and Euler angles of cylinders of the same size in 3D space. Now I want to obtain the 3D coordinates of a line (of given length, representing the axis of the cylinders) passing through the centroid and oriented according to the three Euler angles. What kind of coordinate transformation should I consider?

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I think you'd be better off using regionprops3 to extract the Eigenvalues and Eigenvectors properties of the cylinders, instead of the Orientation property (which I assume you are using now). The eigenvector corresponding to the largest eigenvalue should give you the direction vector of the long axis of the cylinder directly.

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MATLAB: How to rotate points on 2D coordinate systems

Hello,

You can rotate your points with a rotation matrix:

Here's a simple implementation,

% Create rotation matrix
theta = 90; % to rotate 90 counterclockwise
R = [cosd(theta) -sind(theta); sind(theta) cosd(theta)];
% Rotate your point(s)
point = [3 5]'; % arbitrarily selected
rotpoint = R*point;

The rotpoint is the 90 degree counterclockwise rotated version of your original point.

Hope this helps!

MATLAB: Regionprops does not return the correct angle of a line – what am I doing wrong

regionprops on binary looks at 1 values to select the locations to be measured. Your image is mostly 1's, all of the white. You are measuring the properties of the white. You should be using regionprops on ~BW

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MATLAB: How to rotate points on 2D coordinate systems

MATLAB: Regionprops does not return the correct angle of a line – what am I doing wrong

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