名前
CG_Visibility — ポリゴンジオメトリー内のポイント又は辺から可視領域ポリゴンを計算する
概要
geometry CG_Visibility(geometry polygon, geometry point);
geometry CG_Visibility(geometry polygon, geometry pointA, geometry pointB);
説明
観測ポイントまたは pointA と pointB からなる線分から見えるポリゴンの一部が返ります。
Availability: 3.5.0 - SFCGAL >= 1.5.0が必要です。
SFCGAL >= 1.5.0 が必要
このメソッドには SFCGAL バックエンドが必要です。
この関数は3次元に対応し、Z値を削除しません。
この関数は多面体サーフェスに対応しています。
この関数は三角形と不規則三角網 (TIN) に対応しています。
例
穴あきポリゴンの内部のポイントからの可視領域。
コード
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;
出力
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))
図
同じポリゴンの内部の線分からの可視領域。
コード
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;
出力
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))
図