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#464687 - 03/06/17 11:13 ear clipping triangulation of simple polygons
txesmi Offline
User

Registered: 06/13/07
Posts: 979
Loc: Hiporope and its pain
Hi!
A simple polygon has no shared vertex, crossing edges or holes and it is sorted counter-clockwise on right handed coordinates. The algorithm takes three contiguos points, checks the angle between segments and checks if any other point is not contained by the triangle in order to set it as a valid triangle. This method is far from been the fastest but it is pretty easy to follow.


DOWNLOAD
Draw a polygon by mouse left button and triangulate it by mouse right button. You can watch the process by uncommenting SHOW_BUILT definition on 'simple_polygon.h'

Enjoy!

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#464689 - 03/06/17 11:27 Re: ear clipping triangulation of simple polygons [Re: txesmi]
Superku Online
Senior Expert

Registered: 09/13/03
Posts: 6562
Loc: Kiel (Germany)
Very interesting, thanks for sharing!
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#464696 - 03/06/17 13:17 Re: ear clipping triangulation of simple polygons [Re: Superku]
Kartoffel Offline
Expert

Registered: 06/11/09
Posts: 2071
Loc: Bavaria, Germany
cool stuff. can be pretty helpful when filling shapes... I might even need this laugh
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#464698 - 03/06/17 14:17 Re: ear clipping triangulation of simple polygons [Re: Kartoffel]
20BN Offline
Junior Member

Registered: 02/08/03
Posts: 73
Loc: RP China
thanks for sharing!

it's very useful for pathfinding!!!!!!!!!

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#464713 - 03/07/17 06:27 Re: ear clipping triangulation of simple polygons [Re: 20BN]
txesmi Offline
User

Registered: 06/13/07
Posts: 979
Loc: Hiporope and its pain
glad of been helpfull wink

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#464921 - 03/17/17 00:31 Re: ear clipping triangulation of simple polygons [Re: txesmi]
PadMalcom Offline
Serious User

Registered: 03/08/06
Posts: 1987
Loc: Karlsruhe
Cool, how difficult would it be to extend it to handle holes?

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#464941 - 03/18/17 08:20 Re: ear clipping triangulation of simple polygons [Re: PadMalcom]
txesmi Offline
User

Registered: 06/13/07
Posts: 979
Loc: Hiporope and its pain
Originally Posted By: PadMalcom
Cool, how difficult would it be to extend it to handle holes?
As far as I read it is not hard to achieve. It is planned wink

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#464943 - 03/18/17 15:08 Re: ear clipping triangulation of simple polygons [Re: txesmi]
Kartoffel Offline
Expert

Registered: 06/11/09
Posts: 2071
Loc: Bavaria, Germany
Another useful feature would be selecting clockwise/counter-clockwise triangle creation automatically. This should work by adding the relative angles between all lines (of the outline) and checking if the result is greater or less than 0. (theoretically only +360° or -360° are possible).
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