Hi Martin,
You may already know the benchmark done by Erwan's team with some java
implementations
(http://conference.osgeo.org/index.php/foss4g/2008/paper/view/282/177)
It eventually shows the triangulator I have written a few years ago
(available on http://geo.michaelm.free.fr/OpenJUMP/resources/) is very
fast (I have to add it is not 100% robust as it sometimes fails for
large datasets - more than 100k points)
They also wrote a more recent paper about their new implementation for
orbisgis :
http://hal.archives-ouvertes.fr/docs/00/32/95/03/PDF/CDT-paper.pdf
Now about your question :
INPUT
- should be able to input ponctual (sites) , lineal (breaklines),
polygonal geometries (points and breaklines to be extracted)
- collection of coordinates
INPUT/OUTPUT
- in my plugin, I decided that when the input was a single polygon, the
output should be a triangulation containing only triangles inside the
polygon (not all triangles inside the convex hull)
(may not concern the low level api)
OUTPUT
- in my Triangulation class, I decided to return a simple Coordinate[]
array containing n*3 objects (elements 0, 1 and 2 composing the first
triangle...)
I'm not that sure, but I think this structure just contained
references to input coordinates (memory-friendly)
- i would prefer a collection of Linestrings or a collection of Polygons
than a MultiLinestring or MultiPolygon, because I'm not sure a
mutigeometry of one million elements is easy to deal with (spatial
indexation inefficient for example). Moreover, individual geometries can
give the oppurtunity to keep the tin structure with links between
elements represented as attributes, or to compute height, slope,
orientation on every individual triangle and keep them as attributes. I
understand why a Tin structure is interesting (no duplicate), but not a
multi-geometry.
My 2 cents
Michaël
Martin Davis a écrit :
To those that are interested in the upcoming JTS triangulation API, a
question:
What type of input and output structures would you find useful?
Currently I'm developing the following:
INPUT:
- Geometry (from which the site/vertex coordinates are extracted)
- Collection of Coordinates
OUTPUT:
- MultiLineString containing triangulation edges
- GeometryCollection of Polygons containing triangles
You can also work directly with the internal datastructures of the
triangulation (Vertices, QuadEdges, etc), but this requires a higher
level of understanding.
Is there any other option I haven't though of?
_______________________________________________
jts-devel mailing list
[email protected]
http://lists.refractions.net/mailman/listinfo/jts-devel
