Convex "Hull" 2d.................................

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Does anybody know a _very easy_ method to find a “convex hull” for a set of given points in a 2d scenario?

Thank you in advance.

Posted 24-Jan-14 11:55am

idle63

Updated 24-Jan-14 11:56am

v2

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-01-24T12:08:00

Solution 1

It is not quite easy, by the very nature of this problem, but I used the code of AForge.NET and was very satisfied with the quality of results and performance. Please see:
http://en.wikipedia.org/wiki/Aforge.net[^],
http://www.aforgenet.com/[^],
http://www.aforgenet.com/aforge/framework/docs[^].

And here is the convex hull:
http://www.aforgenet.com/framework/docs/html/eb434e52-9781-2f51-f092-8a76db2814b9.htm[^],
http://www.aforgenet.com/framework/docs/html/990cafc5-3613-e13f-615a-f5a7e359f262.htm[^].

I used it as a part of blob recognition, and the hulls of each blob were quite accurate and the whole thing performed in no time — highly recommended.

See also the CodeProject articles by the author of AForge.NET: Andrew Kirillov: http://www.codeproject.com/Articles/Andrew-Kirillov#articles[^].

—SA

Posted 24-Jan-14 12:08pm

Sergey Alexandrovich Kryukov

Updated 24-Jan-14 12:26pm

v2

Comments

[no name] 24-Jan-14 18:15pm

Great to see you coming back in this forum ;) I will check your suggestions immediately.

Thank you very much, kind regards, Bruno

Sergey Alexandrovich Kryukov 24-Jan-14 18:28pm

Hope you will be satisfied and accept the answer formally.
I did not leave anywhere, just very busy so I only paid attention for more interesting posts, like yours. :-)
—SA

[no name] 24-Jan-14 18:45pm

It will take some time to check all these links. But in the meanwhile I will accept your answer "blind", because I trust in you by experience. (+- my english, you know it meanwhile :) )

Kind regards, Bruno

Sergey Alexandrovich Kryukov 24-Jan-14 18:57pm

Of course... you did not have to accept or deny anything in a blindfolded way. Anyway, you can change your mind at any time.
Good luck.
—SA

[no name] 24-Jan-14 19:26pm

I followed your comments and answers for a long time now, and really I learned with each of them! So also with this "easy" question I trust on your recommondations!

It's just hard for my notion that a 2d convex hull is so difficult to determine. I imagine "I'm sitting in the center" and see all the points ..... visually simple .... computationally not really. But I'll stay tuned;)

Kind regards, Bruno...and sometimes I hated you for your comments ;)

http://www.youtube.com/watch?v=vBadAVsdixk

Sergey Alexandrovich Kryukov 24-Jan-14 21:40pm

Thank you for nice piece of music. I'm enjoying it right now, when writing this.

You are right about some difficulty in determination of the hull. I mean, it's pretty easy to define it formally, but algorithmically it's a delicate thing. "See all the points" is not the key. It's related to a simple notion of convex point set in a vector space. It is so basic that the space does not have to be Euclidean: Convex set. And the hull is a bit more difficult to understand: Convex hull. But the algorithm is more difficult thing here...

Sorry, if you didn't like some of my comments, by they are already written, and I still believe that some of them may have sense. And I don't think that hating me could be true or false, rather, it just wouldn't make any sense. For some relaxation, in return: did you hear this piece of music?

I hope you like it... at least, don't switch off before first two minutes... :-)
Some more...
Tell me what do you think...

—SA

[no name] 25-Jan-14 10:13am

Thank you for this beautiful music! The first track reminds me of a very nice Latin American song "Besame Mucho" ... and saxophone is anyway one of the finest instruments. I started to play it four years ago, with little success but with much joy :)

And sorry "hated" was definitely the wrong word, one time more my lack in english..."not agree" does match better.

Finally Convex Hull:
Thanks for the links. With this help I was able to solve it.

Best regards, Bruno

Sergey Alexandrovich Kryukov 25-Jan-14 19:29pm

I'm very glad that you completed the solution (I was pretty much sure you would).
I've read that Besame Mucho (bolero song actually written by young Mexican girl Consuelo Velázquez in 1940) is one of the most performed songs in the world. I heard very many interesting instrumental variations of it. Actually, the melody is pretty far from the piece played by Surman. I discovered this wonderful musician a couple years ago after listening one radio program with a short sample. Glad you like his music. One more great finding: did you ever heard "17 hippies", a German groups? You can find a lot on Youtube... In this case, different pieces are very different, in many different styles and languages...

Best wishes,
—SA