Waiting for PostGIS 2.1 - Delaunay Triangulation with 3D

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Wednesday, September 12. 2012

Posted by Regina Obe in postgis postgresql, waiting_postgis_21

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Waiting for PostGIS 2.1 - Delaunay Triangulation with 3D

Simon commented that it would be really nice if PostGIS had a Delaunay Triangulation function and evidentally a lot of people were thinking that too by the ticket comments. JTS has had it for sometime, and JASPA quickly gave it an SQL interface in their mix since they build directly ontop of JTS. Sandro and I were talking about how much effort and/or money to port this feature from JTS to GEOS and then expose it on PostGIS. Low and behold, Brian Campbell dropped a gift patch on GEOS door and Sandro scurried over to the PostGIS side of the fence to expose it as an SQL function. With the magic of open source, it all came together into a fairly easy to use SQL function that you can also sprinkle with raster if you choose.

In it's initial form, I complained hey - where's my 3D, JASPA has 3D, JTS has 3D, and 3D was added. Ask and you may receive. To get the 3D feature though, you'll need GEOS 3.4.0dev from a day or so ago. If you are on windows and using 64-bit PostgreSQL or PostgreSQL 9.2(both 32-bit and 64-bit), you can use one of the windows build bot builds and follow along.

Example of ST_DelaunayTriangles

Simon did such a good job of using R to build a ST_DelaunayTriangles, that I figured I'd reuse his example a bit, but slightly modified. Using Simon's example from R-Based Delaunay Triangulation Function for PostGIS using Deldir Package , but instead of using R, using the now built-in PostGIS ST_DelaunayTriangles and new closer to SQL/MM semantics of PostGIS 2+.

WITH ds(geom) AS (
SELECT  ST_GeomFromText('POINT Z(-90.2618913358086 33.2184179805337 403)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2534717690058 33.2235960587115 332)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2526790106307 33.2219983038141 393)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2548360643114 33.2220152472292 349)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2569931215599 33.2220321532301 373)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2591702280608 33.2202360124111 329)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2570132117573 33.2202191464654 242)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2548561990173 33.2202022431079 311)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2526991898448 33.2201853023387 296)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2527193654874 33.2183723003489 375)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2548763301557 33.2183892384722 331)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2570332983911 33.2184061391864 246)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2591902701899 33.2184230024914 292)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2602038624534 33.2165408049195 228)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2580468665807 33.2165321889039 295)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2558898738654 33.2165235354584 305)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2537328843112 33.2165148445831 396)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2537432444696 33.2147017821533 329)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.255900189497 33.2147104705514 213)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2580571376854 33.2147191215224 218)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2602140890308 33.2147277350661 226)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.2591415442112 33.2133037851107 310)',4326)
UNION ALL
SELECT ST_GeomFromText('POINT Z(-90.254879330931 33.2133111535788 228)',4326) 
)
SELECT ST_AsText(ST_DelaunayTriangles(ST_Collect(ds.geom)))
  FROM ds ;

The output looks like this, which I haven't verified how different it is from Simon's output since the order is different

  GEOMETRYCOLLECTION Z (
 POLYGON Z ((-90.2618913358086 33.2184179805337 403
,-90.2602140890308 33.2147277350661 226
,-90.2602038624534 33.2165408049195 228
,-90.2618913358086 33.2184179805337 403))
,POLYGON Z ((-90.2618913358086 33.2184179805337 403
,-90.2602038624534 33.2165408049195 228
,-90.2591902701899 33.2184230024914 292
,-90.2618913358086 33.2184179805337 403))
,POLYGON Z ((-90.2618913358086 33.2184179805337 403
,-90.2591902701899 33.2184230024914 292
,-90.2591702280608 33.2202360124111 329
,-90.2618913358086 33.2184179805337 403))
,POLYGON Z ((-90.2618913358086 33.2184179805337 403
,-90.2591702280608 33.2202360124111 329
,-90.2569931215599 33.2220321532301 373
,-90.2618913358086 33.2184179805337 403))
,POLYGON Z ((-90.2569931215599 33.2220321532301 373
,-90.2591702280608 33.2202360124111 329
,-90.2570132117573 33.2202191464654 242
,-90.2569931215599 33.2220321532301 373))
,POLYGON Z ((-90.2569931215599 33.2220321532301 373
,-90.2570132117573 33.2202191464654 242
,-90.2548561990173 33.2202022431079 311
,-90.2569931215599 33.2220321532301 373))
,POLYGON Z ((-90.2569931215599 33.2220321532301 373
,-90.2548561990173 33.2202022431079 311
,-90.2548360643114 33.2220152472292 349
,-90.2569931215599 33.2220321532301 373))
,POLYGON Z ((-90.2569931215599 33.2220321532301 373
,-90.2548360643114 33.2220152472292 349
,-90.2534717690058 33.2235960587115 332
,-90.2569931215599 33.2220321532301 373))
,POLYGON Z ((-90.2534717690058 33.2235960587115 332
,-90.2548360643114 33.2220152472292 349
,-90.2526790106307 33.2219983038141 393
,-90.2534717690058 33.2235960587115 332))
,POLYGON Z ((-90.2526790106307 33.2219983038141 393
,-90.2548360643114 33.2220152472292 349
,-90.2526991898448 33.2201853023387 296
,-90.2526790106307 33.2219983038141 393))
,POLYGON Z ((-90.2591415442112 33.2133037851107 310
,-90.254879330931 33.2133111535788 228
,-90.2580571376854 33.2147191215224 218
,-90.2591415442112 33.2133037851107 310))
,POLYGON Z ((-90.2591415442112 33.2133037851107 310
,-90.2580571376854 33.2147191215224 218
,-90.2602140890308 33.2147277350661 226
,-90.2591415442112 33.2133037851107 310))
,POLYGON Z ((-90.2602140890308 33.2147277350661 226
,-90.2580571376854 33.2147191215224 218
,-90.2602038624534 33.2165408049195 228
,-90.2602140890308 33.2147277350661 226))
,POLYGON Z ((-90.2602038624534 33.2165408049195 228
,-90.2580571376854 33.2147191215224 218
,-90.2580468665807 33.2165321889039 295
,-90.2602038624534 33.2165408049195 228))
,POLYGON Z ((-90.2602038624534 33.2165408049195 228
,-90.2580468665807 33.2165321889039 295
,-90.2591902701899 33.2184230024914 292
,-90.2602038624534 33.2165408049195 228))
,POLYGON Z ((-90.2591902701899 33.2184230024914 292
,-90.2580468665807 33.2165321889039 295
,-90.2570332983911 33.2184061391864 246
,-90.2591902701899 33.2184230024914 292))
,POLYGON Z ((-90.2591902701899 33.2184230024914 292
,-90.2570332983911 33.2184061391864 246
,-90.2591702280608 33.2202360124111 329
,-90.2591902701899 33.2184230024914 292))
,POLYGON Z ((-90.2591702280608 33.2202360124111 329
,-90.2570332983911 33.2184061391864 246
,-90.2570132117573 33.2202191464654 242
,-90.2591702280608 33.2202360124111 329))
,POLYGON Z ((-90.2570132117573 33.2202191464654 242
,-90.2570332983911 33.2184061391864 246
,-90.2548763301557 33.2183892384722 331
,-90.2570132117573 33.2202191464654 242))
,POLYGON Z ((-90.2570132117573 33.2202191464654 242
,-90.2548763301557 33.2183892384722 331
,-90.2548561990173 33.2202022431079 311
,-90.2570132117573 33.2202191464654 242))
,POLYGON Z ((-90.2548561990173 33.2202022431079 311
,-90.2548763301557 33.2183892384722 331
,-90.2527193654874 33.2183723003489 375
,-90.2548561990173 33.2202022431079 311))
,POLYGON Z ((-90.2548561990173 33.2202022431079 311
,-90.2527193654874 33.2183723003489 375
,-90.2526991898448 33.2201853023387 296
,-90.2548561990173 33.2202022431079 311))
,POLYGON Z ((-90.2548561990173 33.2202022431079 311
,-90.2526991898448 33.2201853023387 296
,-90.2548360643114 33.2220152472292 349
,-90.2548561990173 33.2202022431079 311))
,POLYGON Z ((-90.2527193654874 33.2183723003489 375
,-90.2548763301557 33.2183892384722 331
,-90.2537328843112 33.2165148445831 396
,-90.2527193654874 33.2183723003489 375))
,POLYGON Z ((-90.2527193654874 33.2183723003489 375
,-90.2537328843112 33.2165148445831 396
,-90.2537432444696 33.2147017821533 329
,-90.2527193654874 33.2183723003489 375))
,POLYGON Z ((-90.2537432444696 33.2147017821533 329
,-90.2537328843112 33.2165148445831 396
,-90.2558898738654 33.2165235354584 305
,-90.2537432444696 33.2147017821533 329))
,POLYGON Z ((-90.2537432444696 33.2147017821533 329
,-90.2558898738654 33.2165235354584 305
,-90.255900189497 33.2147104705514 213
,-90.2537432444696 33.2147017821533 329))
,POLYGON Z ((-90.2537432444696 33.2147017821533 329
,-90.255900189497 33.2147104705514 213
,-90.254879330931 33.2133111535788 228
,-90.2537432444696 33.2147017821533 329))
,POLYGON Z ((-90.254879330931 33.2133111535788 228
,-90.255900189497 33.2147104705514 213
,-90.2580571376854 33.2147191215224 218
,-90.254879330931 33.2133111535788 228))
,POLYGON Z ((-90.2580571376854 33.2147191215224 218
,-90.255900189497 33.2147104705514 213
,-90.2580468665807 33.2165321889039 295
,-90.2580571376854 33.2147191215224 218))
,POLYGON Z ((-90.2580468665807 33.2165321889039 295
,-90.255900189497 33.2147104705514 213
,-90.2558898738654 33.2165235354584 305
,-90.2580468665807 33.2165321889039 295))
,POLYGON Z ((-90.2580468665807 33.2165321889039 295
,-90.2558898738654 33.2165235354584 305
,-90.2570332983911 33.2184061391864 246
,-90.2580468665807 33.2165321889039 295))
,POLYGON Z ((-90.2570332983911 33.2184061391864 246
,-90.2558898738654 33.2165235354584 305
,-90.2548763301557 33.2183892384722 331
,-90.2570332983911 33.2184061391864 246))
,POLYGON Z ((-90.2548763301557 33.2183892384722 331
,-90.2558898738654 33.2165235354584 305
,-90.2537328843112 33.2165148445831 396
,-90.2548763301557 33.2183892384722 331)))

Now all it needs is an option to expose it as a TIN.

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Regina, Always good to see functionality exposed in the core. Best place for it. Well done. regards Simon

#1 Simon Greener (Homepage) on 2012-09-13 03:08 (Reply)

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