4 Replies Latest reply on Feb 27, 2018 1:23 PM by James Archer

    Measuring distances between points across the surface of a model.

    James Archer

      Hi

       

      I have a an STL model of a human head. I want to measure the distance across the surface of the model between chosen points, the points of interest are based on ratios of head circumference, distance between the ears ect. I have inserted some images to illustrate what I am trying to describe. How do I go about doing this?

       

      10-20-eeg.jpg10-20-map.jpg

      The second challenge I have is once I have selected a bunch of points over the surface of the head from careful measurements over the surface, how do I extract those points and flatten them onto a 2D  plane. In such a way that if you covered part of the head with the 2D plane it would line up with the points of interest on the head like mask.

       

      Previously I have only designed electronics enclosures in Solidworks and I don't have a lot of experience designing or messing around with complex curved models. Any help would be much appreciated, I am in way over my head (excuse the pun).

       

      Kind regards,
      James

        • Re: Measuring distances between points across the surface of a model.
          Kevin Chandler

          Hello,

           

          1. Create planes where your leylines are shown:
          2. On each plane, sketch a rectangle
          3. Using each rectangle, create a planar surface
          4. Using each planar and the top of the head, create an intersection curve
            (I had to Split Entities on my curve because path length dim needs more than one segment, that's why there's a dot midway)
          5. Add a path length dimension to the curve
          6. In Equations dialog:
            1. Create global variables for 10% & 20% of the path length dimension (yellow)
          7. Outboard of a sketch, create ref geometry points
            1. Select the last option in property manager and select the intersection curve
            2. Select Distance and type in any number
            3. Return to Equations and equate the number you entered to the 10% global variable
            4. Add more points, using the multiples of 10% & 10% as needed to get your correct placement.
          8. Repeat adding points for all intersection curves

           

          Note: The approach I used in the equations handling (w/path specific GVs, etc) can be possibly streamlined, but the concept is there.

          [EDIT: one thought on this is to have just a 10% GV for each path and the points' distance will be multiples of this.]

           

          I hope this helps.

           

          Cheers,

           

          Kevin

          SW2017 attached.

          • Re: Measuring distances between points across the surface of a model.
            Elmar Klammer

            Hi James,

             

            Your sections lend themselves to use the segment tool once you have the intersection curve. Easy to see what points you need to connect.

            That gives your your U-line segments without having to go through the equation manager. You have already enough to do. No point bogging yourself down with this awful interface.

             

            The V-line segments are a little trickier. You can use the 3d spline on surface tool (be aware it is one of those SW enhancements that only work your patience. It is unstable to the point you want to go through the roof) or better use regular splines and add 1 or 2 points in between the U-Lines on surface.

             

            To extract the point location you add a 3d sketch. Now place sketch points on every position you like to know the coordinates.

            Export the file to iges.

            Rename the iges file to txt

            Open the text file in notepad. Look for all entries towards the bottom that start with 116

            That are the point coordintates in the last 3D sketch.

             

            To export the flattened U-V sections out you will need SW Premium. Create surface patches and use the surface flatten tool.

            I would not do it on large patches to keep the distortion error down.

             

            Elmar