Re: [Jts-topo-suite-user] Triangulating polygons?

[Martin D. <mb...@re...>]

I agree.  I think it's standard that for a valid triangualation all 
vertices must be used.

Asger Sigurd Skovbo Petersen wrote:
> Hi Michael,
>
> I vote that it is not valid.
>
> A common usage scenario of a polygon triangulator is to be able to
> interpolate a continuous surface from an attribute value on the
> vertices. In a simple case this attribute value could be the Z
> coordinate and the surface could then represent the terrain. 
>
> To be able to do this, all vertices must be used (also colinear).
>
> Best regards
> Asger
>
> -----Original Message-----
> From: Michael Bedward [mailto:mic...@gm...] 
> Sent: 28. april 2010 11:48
> To: jts...@li...
> Subject: Re: [Jts-topo-suite-user] Triangulating polygons?
>
>   
>> Actually this prompts a definitional question: for a triangulation to 
>> be valid must it use all hole vertices (other than co-linear ones) ?
>>
>>     
>
> A little more on this question... Looking at a few geometry papers it
> seems that what constitutes a valid triangulation varies. For instance,
> some papers triangulate convex polygons be adding additional internal
> nodes.
>
> Take this example:
> POLYGON( (50 100, 100 200, 200 0, 100 0, 100 100, 50 100)
>
> Here is the "obvious" minimal triangulation...
> http://imagebin.org/94784
>
> Do we call that a valid triangulation or is the larger triangle branded
> as a quadrilateral ?  I vote that it's valid :)
>
> Michael
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022