On mardi 6 décembre 2016 20:31:57 CET Michael Sumner wrote: > Thanks Even, > > Does a TriangulatedSurface consist of separate Triangles, all with each > three vertices stored explicitly? I.e. is there no shared vertex pool that > primitives use via index?
Yes, the TriangulatedSurface is a collection of separate triangles. No smart optimization here. We stick to the simple features model. > > That seems to be what simple features dictates, but it's unclear to me how > applications should work with it. Is vertex de-duplication to be be done at > each conversion, or is there a way to carry those indexes through? Apart from shapefile/filegdb triangle strip/fan that could be considered as a kind of vertex indexing, the WKT/WKB representation (and thus the exchanges with PostGIS) don't have that. Actually you could retrieve an indexed view of the TIN by using the GDALTriangulationCreateDelaunay() API ( http://www.gdal.org/gdal__alg_8h.html#a498205ae5f4f0ec9f43e5c65bb392060 ), although it is a bit overkill to recompute a triangulation from a set of triangles... (and the triangulation it will return will generally not be the original one) Even > > Cheers, Mike > > On Wed, Dec 7, 2016, 03:22 Even Rouault <[email protected]> wrote: > > Hi, > > > > > > > > This is a call to discuss the proposed RFC 64: Triangle, Polyhedral > > surface and TIN > > > > > > > > https://trac.osgeo.org/gdal/wiki/rfc64_triangle_polyhedralsurface_tin > > > > > > > > ~~~~~ > > > > > > > > Summary: > > > > > > > > As of now, the OGRGeometry class (the base class from which all the > > subtypes are derived) is limited to OGRCompoundCurve, OGRCircularString, > > OGRLinearRing, OGRMultiLineString, OGRMultiPoint, OGRMultiPolygon, > > OGRMultiCurve, OGRSimpleCurve, OGRCurvePolygon and OGRPolygon. > > > > > > > > This RFC addresses the addition of the following new geometries in > > OGRGeometry: > > > > * Triangle - A subset of polygons, the fundamental difference is that it > > is made of 3 nodes only (actually 4, with the last one being the > > repetition > > of the first one) and ONLY ONE exterior boundary and NO interior polygons. > > > > * PolyhedralSurface - A 3D figure made exclusively of Polygons. > > > > * TriangulatedSurface - A subset of PolyhedralSurface; a 3D figure which > > consists exclusively of Triangles. > > > > > > > > ~~~~~ > > > > > > > > I've rebased and extended the work done by Avyav during last GSoc on top > > of current trunk, where it passes our continuous integration tests. I > > think > > we should consider merging it soon as it can easily rot if kept longer in > > a > > branch (the refresh from my previous branch dating to end of August was > > rather painful) > > > > > > > > Even > > > > > > > > -- > > > > Spatialys - Geospatial professional services > > > > http://www.spatialys.com > > _______________________________________________ > > gdal-dev mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com
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