Hi,
How about densify the polygons before applying Delaunay triangulation.
But again, there is no guarantee not to have steinar points.
Yes, I don't know how much you have to densify to guarantee that no
point will be added.
Just a naive question, as I don't know exactly your problem. If you want
to fill the gap
between your polygons, can you use the difference between the polygon
envelope (or
anu surface including your gap) and your polygons ?
Michaël
Brian.
On Mon, Nov 18, 2013 at 10:20 AM, Brian Sanjeewa Rupasinghe
<[email protected] <mailto:[email protected]>> wrote:
Thanks Micheal, good point. Yes, i use JTS Conformal Delaunay
Triangulation with edge enforcement with a small tolerance
(0.001). As you mentioned, it introduces steinar paoints that are
not in the polygons. If i stick with Conformal Delaunay
Triangulation, any solution to overcome
this? Otherwise, i can use your Polygon triangulation to
triangulate space between the two polygons. I think again it might
introduce the same
problem, when deriving the space by subtracting the union of
polygons from the ConvexHull!!!. Any idea is appreciated.
Brian.
On Mon, Nov 18, 2013 at 1:54 AM,
<[email protected]
<mailto:[email protected]>> wrote:
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Today's Topics:
1. Re: Polygon union (Brian Sanjeewa Rupasinghe)
2. Re: Polygon union (Micha?l Michaud)
----------------------------------------------------------------------
Message: 1
Date: Sun, 17 Nov 2013 10:24:50 +0000
From: Brian Sanjeewa Rupasinghe <[email protected]
<mailto:[email protected]>>
Subject: Re: [Jts-topo-suite-user] Polygon union
To: [email protected]
<mailto:[email protected]>
Message-ID:
<CAEMA-4h+_w7o0=eigqfd_s8bg5gunat6cildxga8zf5qpsv...@mail.gmail.com
<mailto:[email protected]>>
Content-Type: text/plain; charset="iso-8859-1"
Hi, Micheal
Thanks for the reply. My use case is to add triangles between
a pair of
polygons to get the amalgam. My polygons are in PostGIS
and what i do is, i get the union of polygon pair with a query
in PostGIS
and output is converted into JTS and triangulated.
Then i find the triangles between them and add all of them
with the union
pair. So the final result should be a polygon which does
not happen always. Where should i exactly apply geometry precision
reduction. Is it only to the union geometry from PostGIS or
do i need to apply it to output triangles as well?
Brian.
On Sat, Nov 16, 2013 at 6:43 PM, Brian Sanjeewa Rupasinghe <
[email protected] <mailto:[email protected]>> wrote:
> Hi,
>
> I need to union adjoining polygons together. I use
UnionWithUnionOp()
> method in JTS 1.13.
> However, sometimes, even if i reduce the geometry precision,
it does not
> end up with a unique polygon resulting a multi-polygon. In
such instances
> which method is the best to
> avoid creating multi-polygon? I used buffer(0), but it did
not work. What
> about adding a small +- buffer?
>
> Brian.
>
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Message: 2
Date: Sun, 17 Nov 2013 12:26:57 +0100
From: Micha?l Michaud <[email protected]
<mailto:[email protected]>>
Subject: Re: [Jts-topo-suite-user] Polygon union
To: [email protected]
<mailto:[email protected]>
Message-ID: <[email protected]
<mailto:[email protected]>>
Content-Type: text/plain; charset="iso-8859-1"
Hi,
Do you use a constrained triangulation or not ?
How do you find triangles between your polygons ?
Possible problems I can see are :
Triangulation without constraint : some triangles may be
partly on your polygon (green) and partly in the gap (blue)
Triangulation with constraint : triangles "seem" to fill the gap,
but some vertices are not part of the original polygons.
Depending on
how you find the triangles lying in the gap, you may miss some.
Micha?l
> Hi, Micheal
>
> Thanks for the reply. My use case is to add triangles
between a pair
> of polygons to get the amalgam. My polygons are in PostGIS
> and what i do is, i get the union of polygon pair with a
query in
> PostGIS and output is converted into JTS and triangulated.
> Then i find the triangles between them and add all of them
with the
> union pair. So the final result should be a polygon which does
> not happen always. Where should i exactly apply geometry
precision
> reduction. Is it only to the union geometry from PostGIS or
> do i need to apply it to output triangles as well?
>
> Brian.
>
>
> On Sat, Nov 16, 2013 at 6:43 PM, Brian Sanjeewa Rupasinghe
> <[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>> wrote:
>
> Hi,
>
> I need to union adjoining polygons together. I
> use UnionWithUnionOp() method in JTS 1.13.
> However, sometimes, even if i reduce the geometry
precision, it
> does not end up with a unique polygon resulting a
multi-polygon.
> In such instances which method is the best to
> avoid creating multi-polygon? I used buffer(0), but it
did not
> work. What about adding a small +- buffer?
>
> Brian.
>
>
>
>
>
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