Orientation of multiple 3D particles

Hi,

I have a stack of uCT data, labelled into multiple particles. I would like to get the orientation of the particles (whereever it is the ellipsoid principle direction, or Feret angle) relating to XY plane. Does anyone know how I can get these information (better in a structure of a table) ?

Thanks,
Peleg

Hi Peleg,

You may want to try the ellipsoid fitting plugin :
http://imagejdocu.tudor.lu/doku.php?id=plugin:analysis:3d_analysis:start

do not hesitate if you have questions or comments,

best,

Thomas

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Thank you Thomas ! :slight_smile:
This plug-in indeed solves the problem. For multiple objects the calculation could be very long - but the table of results is shown at the end.

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One more question regarding the results of the “ellipsoid fitting”. I noticed that the angles with the planes are of the range [0,90], and not [-90,90]. Just to be sure - my question is if I can determine the sign of an angle, e.g. with XY plane by the Vz coordinate of the main elongation axis ? i.e. when Vz is negative - then the angle is negative too ?

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Hi Peleg,

Yes since the plane has no orientation all angles are between 0 and 90, you need to compute then the scalar vector between one vector of the plane and your vector, if it >0 then it is 0-90 else it is 90-180. Maybe I will add this information in the next release of the plugin. Do not hesitate if you need help to compute this.

Best,

Thomas

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