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Subject: [ggl] [Fwd: [postgis-devel] PolyhedralSurface - PostGIS 2.0]
From: Mateusz Loskot (mateusz)
Date: 2010-01-22 19:58:23


This post may be of interest whoever is into 3D support in GGL.

-------- Original Message --------
Subject: [postgis-devel] PolyhedralSurface - PostGIS 2.0
Date: Fri, 22 Jan 2010 12:24:21 +0100
From: Olivier Courtin <olivier.courtin_at_[hidden]>
Reply-To: PostGIS Development Discussion
To: PostGIS Development Discussion <postgis-devel_at_[hidden]>


I've just began to (re)work on PolyhedralSurface type support for
future 2.0 branch,
before to spend more time on this, i wanted to check with you i have
green light to
go on further.

Any comments/reactions are welcomed !

Targeted usage: City Modelisation (LOD 0 to LOD 3)

Some current thoughts about implementation:

- Removing unused Integer types (POINTYPEI, LINESTINGTYPEI,
  to have 3 news types availables.

- Add PolyhedralSurface type (cf SFS 1.2 and SQL/MM3)
  EWKT look like
  POLYHEDRALSURFACE(((0 0 0,0 1 0,1 1 0,0 0 0)),((0 0 0,1 0 0,1 0 1,0
0 1,0 0 0)),...)

  So a bit like a 3DZ MULTIPOLYGON except that:
  - every polygon mean a face (with all points on the same plan, and
    self intersection)
  - only one ring by polygon/face (i.e no hole)
  - points must be defined couterclockwise
  - Each face must be connected to the previous/next ones at least by
a point

  And resulting PolyhedralSurface must be convex (and without hole)

- Don't use GEOS for common function on this type (as it 'only' handle
  but implement in liblwgeom 3D primitives:
      - ST_IsValid
      - Point in Polyhedra test (and so others related 9DIM functions)
      - Polyhedra minimal distance (to a point also to an another
      - ST_Centroid
      - ST_Volume

- I/O functions
      - extensions to GML and KML
      - CityGML
      - Collada
      - X3D ?

- Check with others PostGIS Z dim compliants functions that this new
   is rightly supported

- 3D Index issue (not even explore this point)

- Futures issues (to reach LOD 2 and 3):
    - How to link a geometry to a texture
    - How to handle Level Of Details (for example in CityGML)

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Mateusz Loskot,
Charter Member of OSGeo,

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