topic Re: The way connect all points? in .NET Forum

The way connect all points?

Anonymous — Thu, 29 Jun 2017 11:36:35 GMT

How to connect the all points on a plane in the shortest and non cross way?

For example,i want to connect the points below in the shortest and non cross way.Does anyone can give me a solution?

Thanks a lot.

Re: The way connect all points?

3wood — Thu, 29 Jun 2017 12:01:24 GMT

Create a triangle from leftmost 3 points. Then search towards right for the closest point and form the second triangle. You will link all points with triangles at the end. Then the outmost boundary is the result.

Re: The way connect all points?

Anonymous — Fri, 30 Jun 2017 19:27:35 GMT

Hi,

I believe the algorythm you are looking for is "convex hull".

You can add GeoNet API via nuget and use its whole bunch of geoprocessing algorythms, you just need to pass geometry from cad entities to API methods then return the results to the autocad world.

Re: The way connect all points?

_gile — Fri, 30 Jun 2017 19:50:52 GMT

kacarikalen a écrit :

Hi,

I believe the algorythm you are looking for is "convex hull".

You can add GeoNet API via nuget and use its whole bunch of geoprocessing algorythms, you just need to pass geometry from cad entities to API methods then return the results to the autocad world.

Hi,

A convex hull won't connect all points, precisely because it's convex:

You can find an AutoCAD .NEt implementation of Convex Hull here.

Re: The way connect all points?

Anonymous — Fri, 30 Jun 2017 19:59:49 GMT

Yes, it needs sweeping line method like graham scan, like the form of creating delaunay triangulation then deleting the innermost edges.

Some of them can be found here:

https://gis.stackexchange.com/questions/5426/finding-boundary-co-ordinates-from-given-set-of-point-co-ordinates

Re: The way connect all points?

hgasty1001 — Sun, 02 Jul 2017 03:30:54 GMT

Hi,

I think you may find the paper in the following link very useful;Beta-Skeleton that paper explain two algorithms to solve the "follow the points" puzzles. As other mentioned this is a kind of concave hull, but it's not as easy as convex hull (Graham scan can be coded in no more than 200 lines o so) . Beta-Skeleton and Crust algorithms relays on Voronoi diagram or Delaunay triangulation in order to find the border of a concave shape. Voronoi is usually implemented using Fortune's algorithm, it's a complicated algorithm based on properties of the parabola curve, but there are some good C# code you can find, for example this: Fortune's Algorithm, so you only need to understand and code for the Beta-Skeleton or Crust as the hardest part it's Voronoi/Delaunay.

Gaston Nunez

Re: The way connect all points?

vaughan.giles7AGEV — Wed, 15 Jan 2025 20:14:29 GMT

I appreciate your post @_gile , thank you.

I do not however understand how to correctly load your customization(s) into Civil 3D - is there a proper help file somewhere that describes the process?

Thanks!

Re: The way connect all points?

norman.yuan — Wed, 15 Jan 2025 20:36:50 GMT

The code @_gile referred to his post is AutoCAD .NET API code. If you want to use/try it, you need to create a AutoCAD plugin project with Visual Studio, which is a .NET Framework, or .NET 8 class library (depending on your AutoCAD being 2025, or prior to 2025), and build the project as AutoCAD .NET plugin DLL. Then you load the DLL into AutoCAD (via command "NETLOAD", or other loading means of your choice). After all these are done, you can run the command defined in the code "Test". So, if you do not know how to write code and create AutoCAD plugin, it is tall task to do😂. and you may need someone to do it for you, or you can get started to learn the basic to just get this code built as DLL, which may only take you a day or two to learn the very basic and get started (then you probably would not want to stop any more!).

Re: The way connect all points?

_gile — Wed, 15 Jan 2025 21:51:24 GMT

@vaughan.giles7AGEV

I replied the same question in Github and TheSwamp.

Re: The way connect all points?

vaughan.giles7AGEV — Wed, 15 Jan 2025 21:53:16 GMT

Thank you @_gile - for those of you interested, here is a link to the AutoLISP version of the routine http://www.theswamp.org/index.php?topic=31865.new;topicseen#new