I have added a new command to the triangulation program
to creates a boundary (concave hull) around the point set.
As you know there is no single solution to this problem.
However based on this paper:
Efficient generation of simple polygons for characterizing the shape of a set of points in the planeby Matt Duckham, Lars Kulik, Mike Worboys, Antony Galton
I have come up with a dynamic way to get a solution by
varying the length parameter from 0.1 to 1 and displaying
the resulting polygon. You start with parameter set at 0.5
pressing "+" keys erodes the hull more, while minus erodes
less.
Of course when the parameter is equal to 1 what you have is
the Convex Hull.
Pressing "ENTER" or "SPACE BAR" or "LEFT-CLICK" will
accept the new Boundary, and the 3dface outside of it
will be deleted.
Pressing "RIGHT-CLICK" will cancel the operation.
There is room for optimization, but the speed ain't bad.
ymg