[PostGIS] #5818: CG_IsSolid(geom) gives the wrong result In PostGIS
PostGIS
trac at osgeo.org
Thu Jan 9 03:54:22 PST 2025
#5818: CG_IsSolid(geom) gives the wrong result In PostGIS
-----------------------+---------------------------
Reporter: nbvfgh | Owner: lbartoletti
Type: defect | Status: new
Priority: critical | Milestone: PostGIS 3.6.0
Component: sfcgal | Version: 3.5.x
Resolution: | Keywords:
-----------------------+---------------------------
Changes (by nbvfgh):
* milestone: PostGIS SFCGAL => PostGIS 3.6.0
Old description:
> We perform the following query on a closed polyhedralsurface:
>
> {{{
> WITH polyhedralsurface AS (
> SELECT
> 'POLYHEDRALSURFACE Z (((-1 1 -1,1 1 -1,1 -1 -1,-1 -1 -1,-1 1
> -1)),
> ((-1 1 1,-1 -1 1,1 -1 1,1 1 1,-1 1 1)),
> ((-1 1 -1,-1 1 1,1 1 1,1 1 -1,-1 1 -1)),
> ((1 1 -1,1 1 1,1 -1 1,1 -1 -1,1 1 -1)),
> ((1 -1 -1,1 -1 1,-1 -1 1,-1 -1 -1,1 -1
> -1)),
> ((-1 -1 -1,-1 -1 1,-1 1 1,-1 1 -1,-1 -1
> -1)))'
> geom
> )
> SELECT
> CG_IsSolid(geom),
> ST_IsClosed(geom),
> CG_Volume(geom)
> FROM polyhedralsurface
>
> -- result : {f,t,0}
> }}}
>
> But when we converted this polyhedralsurface into a solid, we obtained an
> unexpected result
> {{{
> WITH solid AS (
> SELECT CG_MakeSolid(
> 'POLYHEDRALSURFACE Z (((-1 1 -1,1 1 -1,1 -1 -1,-1 -1 -1,-1 1
> -1)),
> ((-1 1 1,-1 -1 1,1 -1 1,1 1 1,-1 1 1)),
> ((-1 1 -1,-1 1 1,1 1 1,1 1 -1,-1 1 -1)),
> ((1 1 -1,1 1 1,1 -1 1,1 -1 -1,1 1 -1)),
> ((1 -1 -1,1 -1 1,-1 -1 1,-1 -1 -1,1 -1
> -1)),
> ((-1 -1 -1,-1 -1 1,-1 1 1,-1 1 -1,-1 -1
> -1)))'
> ) geom
> )
> SELECT
> CG_IsSolid(geom),
> ST_IsClosed(geom),
> CG_Volume(geom)
> FROM solid;
>
> -- expected : {t,t,8};
> -- actual : {f,t,8};
> }}}
> It should be noted that, CG_Volume(geom) computes the volume of a 3D
> solid,and if it applied to surface (even closed) geometries will return
> 0. Its return value is 8 here, indicating that geom is not a surface,
> while CG_IsSolid(geom) returns false. So what type of geometry is geom?
>
> Version Info:
>
> {{{
> POSTGIS="3.5.0 3.5.0" [EXTENSION] PGSQL="170" GEOS="3.13.0-CAPI-1.19.0"
> SFCGAL="SFCGAL 1.5.2, CGAL 5.6.1, BOOST 1.84.0" PROJ="8.2.1
> NETWORK_ENABLED=OFF URL_ENDPOINT=https://cdn.proj.org
> USER_WRITABLE_DIRECTORY=C:\WINDOWS\ServiceProfiles\NetworkService\AppData\Local/proj
> DATABASE_PATH=C:\Program
> Files\PostgreSQL\16\share\contrib\postgis-3.4\proj\proj.db" (compiled
> against PROJ 8.13.0) LIBXML="2.12.5" LIBJSON="0.12" LIBPROTOBUF="1.2.1"
> WAGYU="0.5.0 (Internal)" TOPOLOGY
> }}}
New description:
We perform the following query on a closed polyhedralsurface:
{{{
WITH polyhedralsurface AS (
SELECT
'POLYHEDRALSURFACE Z (((-1 1 -1,1 1 -1,1 -1 -1,-1 -1 -1,-1 1 -1)),
((-1 1 1,-1 -1 1,1 -1 1,1 1 1,-1 1 1)),
((-1 1 -1,-1 1 1,1 1 1,1 1 -1,-1 1 -1)),
((1 1 -1,1 1 1,1 -1 1,1 -1 -1,1 1 -1)),
((1 -1 -1,1 -1 1,-1 -1 1,-1 -1 -1,1 -1 -1)),
((-1 -1 -1,-1 -1 1,-1 1 1,-1 1 -1,-1 -1
-1)))'
geom
)
SELECT
CG_IsSolid(geom),
ST_IsClosed(geom),
CG_Volume(geom)
FROM polyhedralsurface
-- result : {f,t,0}
}}}
But when we converted this polyhedralsurface into a solid, we obtained an
unexpected result
{{{
WITH solid AS (
SELECT CG_MakeSolid(
'POLYHEDRALSURFACE Z (((-1 1 -1,1 1 -1,1 -1 -1,-1 -1 -1,-1 1 -1)),
((-1 1 1,-1 -1 1,1 -1 1,1 1 1,-1 1 1)),
((-1 1 -1,-1 1 1,1 1 1,1 1 -1,-1 1 -1)),
((1 1 -1,1 1 1,1 -1 1,1 -1 -1,1 1 -1)),
((1 -1 -1,1 -1 1,-1 -1 1,-1 -1 -1,1 -1 -1)),
((-1 -1 -1,-1 -1 1,-1 1 1,-1 1 -1,-1 -1
-1)))'
) geom
)
SELECT
CG_IsSolid(geom),
ST_IsClosed(geom),
CG_Volume(geom)
FROM solid;
-- expected : {t,t,8};
-- actual : {f,t,8};
}}}
It should be noted that, CG_Volume(geom) computes the volume of a 3D
solid,and if it applied to surface (even closed) geometries will return 0.
Its return value is 8 here, indicating that geom is not a surface, while
CG_IsSolid(geom) returns false. So what type of geometry is geom?
Version Info:
{{{
POSTGIS="3.6.0dev 3.5.0-91-g593df9088" [EXTENSION] PGSQL="170"
GEOS="3.13.0-CAPI-1.19.0" SFCGAL="SFCGAL 1.5.2, CGAL 5.6.1, BOOST 1.84.0"
}}}
--
--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5818#comment:1>
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