
Re: Calculating the area of a closed 3D path or ring
Posted:
Mar 16, 2013 3:27 AM


On Mar 14, 9:36 pm, Math Guy <M...@Guy.com> wrote: > Ray Koopman wrote: >> >> You haven't said whether the ordering of the points around the >> loop is given or not. > > The user will specify the markers to be used (there are other markers > on the heart which will not be involved in this ring). A routine will > identify the order by picking one point and then determine which of > the remaining points is closest, and will piecewise work it's way > around the ring. This should avoid any errors if the user gives the > order incorrectly. > >> Also, what do you want to do if the loop is not convex? > > Do you mean what if the loop looks like a potato chip with a bite taken > out of it? > > I don't see how that would affect the proposed area calculation method.
It won't affect the plane of best fit, but it may make it harder to identify the loop. I would give the 2D coordinates to a convex hull routine. If the hull uses all the points then it's your loop. But if some points are inside the hull then a simple nearestneighbor approach can sometimes connect the points in the wrong order.

