J'essaie de construire un diagramme voronoi à partir d'une grille de points en utilisant du code modifié d' ici . Il s'agit d'une requête SQL après mes modifications:
DROP TABLE IF EXISTS example.voronoi;
WITH
-- Sample set of points to work with
Sample AS (SELECT ST_SetSRID(ST_Union(geom), 0) geom FROM example."MeshPoints2d"),
-- Build edges and circumscribe points to generate a centroid
Edges AS (
SELECT id,
UNNEST(ARRAY['e1','e2','e3']) EdgeName,
UNNEST(ARRAY[
ST_MakeLine(p1,p2) ,
ST_MakeLine(p2,p3) ,
ST_MakeLine(p3,p1)]) Edge,
ST_Centroid(ST_ConvexHull(ST_Union(-- Done this way due to issues I had with LineToCurve
ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p1,p2),ST_MakeLine(p2,p3)))),'LINE','CIRCULAR'),15),
ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p2,p3),ST_MakeLine(p3,p1)))),'LINE','CIRCULAR'),15)
))) ct
FROM (
-- Decompose to points
SELECT id,
ST_PointN(g,1) p1,
ST_PointN(g,2) p2,
ST_PointN(g,3) p3
FROM (
SELECT (gd).Path id, ST_ExteriorRing((gd).geom) g -- ID andmake triangle a linestring
FROM (SELECT (ST_Dump(ST_DelaunayTriangles(geom))) gd FROM Sample) a -- Get Delaunay Triangles
)b
) c
)
SELECT ST_SetSRID((ST_Dump(ST_Polygonize(ST_Node(ST_LineMerge(ST_Union(v, ST_ExteriorRing(ST_ConvexHull(v)))))))).geom, 2180)
INTO example.voronoi
FROM (
SELECT -- Create voronoi edges and reduce to a multilinestring
ST_LineMerge(ST_Union(ST_MakeLine(
x.ct,
CASE
WHEN y.id IS NULL THEN
CASE WHEN ST_Within(
x.ct,
(SELECT ST_ConvexHull(geom) FROM sample)) THEN -- Don't draw lines back towards the original set
-- Project line out twice the distance from convex hull
ST_MakePoint(ST_X(x.ct) + ((ST_X(ST_Centroid(x.edge)) - ST_X(x.ct)) * 2),ST_Y(x.ct) + ((ST_Y(ST_Centroid(x.edge)) - ST_Y(x.ct)) * 2))
END
ELSE
y.ct
END
))) v
FROM Edges x
LEFT OUTER JOIN -- Self Join based on edges
Edges y ON x.id <> y.id AND ST_Equals(x.edge,y.edge)
) z
Ci-dessous - résultat de ma requête.
Comme vous pouvez le voir, j'obtiens un diagramme de voronoi «presque» correct, sauf les points en surbrillance qui n'ont pas de polygone unique. Voici ce que l'algorithme QGIS produit et ce que j'aimerais obtenir de la requête. Des suggestions où est le problème avec mon code?