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[James <>]

OK thanks Ben. I'll give it a shot and report back.

On Dec 24, 2011 1:33 AM, "Ben Supnik [via cgal-discuss]" <[hidden email]> wrote:

Hi James,

Hrm - well, it won't be fast but you I suppose you can do a "join" on a
huge list of triangles (turn each triangle into a polygon_2 and join
them into a general polygon set).  Then use CGAL to re-triangulate the
resulting output polygons with holes.

If you were already trying this and got orientation errors you'll need
to hand-check your triangles - call orientation() on each triangle - if
it is clockwise, reverse its vertex order; if it is collinear you'll
need to throw it out - CGAL doesn't like degenerate geometry.

(This is in line with your current approach I think.)

It looks like others have discussed going from polygon-with-holes back
to triangulation.

http://stackoverflow.com/questions/406301/polygon-triangulation-with-holes#406647

Note that you'll need an exact constructions kernel, and you'll hit a
speed penalty for that.

cheers
Ben

On 12/23/11 7:20 PM, James Swift wrote:

> No meta data is really required after the merge, just a new list of triangles.
> I suppose, optimally an opengl like triangle-list would be better than
> each triangle described individually where vertices of shared edges
> would be needlessly repeated.
>
>
> On 24 December 2011 01:00, Ben Supnik<[hidden email]>  wrote:
>> Sorry, one more q: is it important to track either whether a result triangle
>> is from an "overlap" and/or which source triangle (or triangle list) the
>> triangle comes from)?
>>
>> The more of this "meta data" you care about, the more complex the
>> implementation I suspect...
>>
>>
>>
>>
>> On 12/23/11 6:49 PM, James wrote:
>>>
>>> Hi,
>>>
>>> I am trying to merge a list of 2d triangles that may or may not overlap
>>> into
>>> a new list of triangles that no longer overlap.
>>>
>>> E.g. two overlapping triangles T1 and T2 merge to create 8 new smaller
>>> triangles
>>>
>>> http://i.imgur.com/WvXaO.png
>>>
>>> (ignore the colours)
>>>
>>> I tried out the example Boolean_set_operations_2/sequence.cpp and then
>>> modified it as it seemed to be what I want to do but my simple changes
>>> resulted in an orientation error. I'm somewhat out of my depth here.
>>>
>>> Can someone experienced with CGAL give me a small example of how this
>>> might
>>> be achieved and what problems I might encounter. I suspect it should be a
>>> simple problem.
>>>
>>> thanks,
>>>
>>> James
>>>
>>>
>>> --
>>> View this message in context:
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>>>
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