Namn
CG_Visibility — Beräkna en synlighetspolygon från en punkt eller ett segment i en polygongeometri
Synopsis
geometry CG_Visibility(geometry polygon, geometry point);
geometry CG_Visibility(geometry polygon, geometry pointA, geometry pointB);
Beskrivning
Returns the portion of a polygon visible from an observer point, or from the observer segment defined by pointA and pointB.
Tillgänglighet: 3.5.0 - kräver SFCGAL >= 1.5.0.
Kräver SFCGAL >= 1.5.0
Denna metod behöver SFCGAL-backend.
Denna funktion stöder 3d och kommer inte att tappa z-index.
Denna funktion stöder polyedriska ytor.
Denna funktion stöder trianglar och triangulerade oregelbundna nätverksytor (TIN).
Exempel
Visibility from a point inside a polygon with holes.
WITH data AS (
SELECT 'POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150))'::geometry AS polygon,
'POINT(91 87)'::geometry AS observer
)
SELECT ST_Collect(polygon, observer) AS input_scene,
CG_Visibility(polygon, observer) AS visibility
FROM data;
GEOMETRYCOLLECTION(POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150)), POINT(91 87)) | POLYGON((78.5 68,98.5 68,108 43.93333333333334,108 98,121.96219931271477 107.03436426116838,107 106.5,107 135,97.5 106.5,65.28017241379311 105.09913793103448,77.5 96.5,78.5 68))
Visibility from a segment inside the same polygon.
WITH data AS (
SELECT 'POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150))'::geometry AS polygon,
'LINESTRING(78.5 68,98.5 68)'::geometry AS observer
)
SELECT ST_Collect(polygon, observer) AS input_scene,
CG_Visibility(polygon,
ST_StartPoint(observer),
ST_EndPoint(observer)) AS visibility
FROM data;
GEOMETRYCOLLECTION(POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150)), LINESTRING(78.5 68,98.5 68)) | POLYGON((78.5 68,98.5 68,100.5 36,101.28125 23.5,111.7109375 23.5,108 36,108 98,110.73389524382901 106.63335340156533,107 106.5,107 157.5,108.51955307262571 173.5,95.75974025974025 173.5,97.5 106.5,70.9811529933481 105.3470066518847,77.5 96.5,78.5 68))