Measuring angles between two fixed points on an imported 3D scan of Humeri


#1

For a research project I need to measure the degrees of variation in the axes of humeri from 3D scans. To do this I need to ‘draw a line’ through a specific point on the head of the humerus and another line through a specific point on the distal axis. I then need to measure the angle of torsion between these two reference lines. I don’t know how to go about this using Rhinoceros 3D so any help, or descriptions would be hugely appreciated.


(Pascal Golay) #2

If you can post an example file - the simpler the better - we can probably help.

-Pascal


#3

Unfortunately it’s not letting me upload the file, but if it helps it’s a 3d scan of a humerus, scanned with a next engine 3d scanner and aligned etc using scan studio.

For a descriptive example, analogously if it were cylinder with a cross bar at both ends I want to measure the angle of variation between the two cross bars.

Thanks for getting back to me.


(Pascal Golay) #4

If it is a point cloud, I guess I’d use the Line command snapping to two ‘representative’ points at each end, then select the lines and run the Angle command. I’m not sure if that fills the bill here or not but it might. In a dense set of points, nailing the one you want might be hard - I’d switch the view to a parallel projection ( not persopective) and it may help, again assuming a point cloud, to use the PointCloud command to remove a few points and hide the main point cloud.

-Pascal


#5

Thanks, I think that’s pretty much what I’ve stumbled upon, I’m currently drawing a triangle over the head and distal end with the diagonal as the reference point then using the ‘Dimension angle’ function to work out the variation.

Does that sound like it makes sense?

I’ll definitely try the parallel view though, that’s some of the trouble I’m having because I try to draw the triangle, but it maps onto the background instead of the object and its hard to determine which way to move it in order to line it all up.

Thanks for the help though!


(Pascal Golay) #6

Just keep in mind that DimAngle is a 2d dimension- it will project the lines to the current CPlane before measuring; the Angle command is not constrained this way- the angle is returned as a print out on the command line. (You may need to scroll up or click and drag the command area deeper.)

-Pascal


#7

Thank you, I’ll try that now.