make polygons from points extracted by concave hull

Question

I would like to make a file including polygon or lines from boundary points extracted from point cloud by concave hull method as shown in below page.

http://ait-survey.com/wp-content/uploads/2015/08/concave_hull_polygon1.png

Boundary points are 3D coordinates.

Also I would like to make polygon file import in AutoCAD.

Let me know how to make it.

Answer 1

That's a interesting problem. I would start with:

1. Identify the outer circle around the points, as shown here: http://through-the-interface.typepad.com/through_the_interface/2011/02/creating-the-smallest-possible-circle-around-2d-autocad-geometry-using-net.html
2. Run through the circle degrees (0 to 2PI), find the closest point. That should give you the order of the points, counter-clockwise.
3. Draw the polyline

I do not have a code 'ready-to-use'... may have some time late this week. But what do you think about the approach?