13 Replies Latest reply: Apr 7, 2017 9:59 AM by ckeller RSS

    Just for fun:

      You are handed a sphere and asked to find the radius. How many data points are required to find the radius, how would you then derive the radius from them and find the location of the radius relative to those points in Pro/E?
        • RE: Just for fun:
          Man, you guys are no fun at all....... Am I posting things no one even wants to think about?
          • Re: Just for fun:
            FrankS.Schiavone Platinum

            Man, this is funny, I'd forgotten I'd started this under a different name way back in the day. Interesting.

            • Re: Defining a sphere.
              ckeller Bronze

              Funny this conversation was from 10 years ago.... hahaha.


              you only need 2 points if you already know it's a sphere.

              All axes that are perpendicular to the surface of a sphere will go through the center of that sphere.

              Since all axes go through the center, then any 2 will intersect at the center.

              Therefore, you only need 2 such points to define 2 such axes to find the center. 

              Then you can measure from that intersecting point to either of the 2 points on the surface, and you will have your radius.

              However in order to define a sphere from points, you'd need 4 points. 

              Of course, not just any 4 points, you'd need 4 points that are not all coplanar, or colinear, or coincident.

              It won't work if any 3 points lie on a line, or if all 4 are co-planar, or if any of the points are coincident.

              2 points define a line

                 or a point if they are coincident.

              3 points define a plane unless they all lie on the same line

                 or a line if they are all colinear

              4 points define a sphere

                 or a plane if they are all coplanar

                 of a line if they are all colinear