[SCM] PostGIS branch master updated. 3.7.0beta1-127-g5852e7ad50
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- Log -----------------------------------------------------------------
commit 5852e7ad5043d7cdb6367ad31a85b3b847b6f9ee
Merge: 56a92ee3a0 65fff31fac
Author: Darafei Praliaskouski <komzpa at gmail.com>
Date: Tue Jul 28 07:18:48 2026 -0700
Merge pull request 'doc(sfcgal): document skeleton functions dropping Z' (!584) from Komzpa/postgis:codex/trac-4323-20260728 into master
The SFCGAL reference claims that straight-skeleton processing supports Z, while current `CG_StraightSkeleton`, `CG_ApproximateMedialAxis`, and their legacy `ST_*` aliases all return 2D output for 3D input.
Document the dimensional behavior consistently for the current and legacy functions. Add regression coverage that fixes the 2D result as the documented contract, and record the correction in `NEWS`.
Closes https://trac.osgeo.org/postgis/ticket/4323
Reviewed-on: https://gitea.osgeo.org/postgis/postgis/pulls/584
commit 65fff31faccef2585206b8aabebe4bd3cdc43eb2
Author: Darafei Praliaskouski <me at komzpa.net>
Date: Tue Jul 28 07:40:14 2026 +0400
doc(sfcgal): document skeleton functions dropping Z
Both straight skeleton and approximate medial axis ignore input Z and return 2D geometries. Add regression coverage for the current CG APIs and make the deprecated ST aliases explicit.
Closes #4323
diff --git a/NEWS b/NEWS
index 3d458547cb..d22b4a48c8 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,8 @@ These are only changes since 3.7.0beta1.
stopwatches, so it no longer fails at random under CI load
(Darafei Praliaskouski)
+ - #4323, GT-584, [sfcgal] Document that straight-skeleton and approximate-medial-axis
+ functions ignore input Z and return 2D geometries (Darafei Praliaskouski)
- GT-545, Fix FlatGeobuf geometry, property, and spatial-index byte order on
big-endian platforms (Darafei Praliaskouski)
- [raster] Fix invalid reads in raster band initialization and
diff --git a/doc/reference_sfcgal.xml b/doc/reference_sfcgal.xml
index 7d11d2af0f..9b61927f27 100644
--- a/doc/reference_sfcgal.xml
+++ b/doc/reference_sfcgal.xml
@@ -2084,8 +2084,9 @@ FROM data;</programlisting>
</para>
<para role="availability" conformance="3.5.0">Availability: 3.5.0</para>
<para role="sfcgal_requirement" conformance="1.3.8">Requires SFCGAL >= 1.3.8 for option use_distance_as_m</para>
+ <note><para>This function ignores the Z dimension.
+It always gives a 2D result even when used on a 3D geometry.</para></note>
<para>&sfcgal_required;</para>
- <para>&Z_support;</para>
<para>&P_support;</para>
<para>&T_support;</para>
</refsection>
diff --git a/doc/reference_sfcgal_legacy.xml b/doc/reference_sfcgal_legacy.xml
index e70cfd5ae5..d12c56bd50 100644
--- a/doc/reference_sfcgal_legacy.xml
+++ b/doc/reference_sfcgal_legacy.xml
@@ -242,6 +242,9 @@
<warning>
<para><function>ST_StraightSkeleton</function> is deprecated as of 3.1.0. Use <xref linkend="CG_StraightSkeleton" /> instead.</para>
</warning>
+ <note><para>Like <function>CG_StraightSkeleton</function>, this
+ function ignores the Z dimension and always gives a 2D result,
+ even when used on a 3D geometry.</para></note>
<para role="availability" conformance="2.1.0">Availability: 2.1.0</para>
<para>&sfcgal_required;</para>
</refsection>
@@ -265,6 +268,9 @@
<warning>
<para><function>ST_ApproximateMedialAxis</function> is deprecated as of 3.5.0. Use <xref linkend="CG_ApproximateMedialAxis" /> instead.</para>
</warning>
+ <note><para>Like <function>CG_ApproximateMedialAxis</function>,
+ this function ignores the Z dimension and always gives a 2D
+ result, even when used on a 3D geometry.</para></note>
<para role="availability" conformance="2.2.0">Availability: 2.2.0</para>
<para>&sfcgal_required;</para>
</refsection>
diff --git a/sfcgal/regress/regress_sfcgal.sql b/sfcgal/regress/regress_sfcgal.sql
index bc3af1e574..bc9e61a110 100644
--- a/sfcgal/regress/regress_sfcgal.sql
+++ b/sfcgal/regress/regress_sfcgal.sql
@@ -75,6 +75,9 @@ SELECT 'CG_3DUnion (aggregate)', ABS(CG_Volume(CG_3DUnion(g))) - 40 < 1e-12 FROM
SELECT CG_Extrude(ST_GeomFromText('POLYGON((-1 -1 -2, 1 -1 -2, 1 1 -2, -1 1 -2, -1 -1 -2))'), 0, 0, 4) AS g
) AS f;
SELECT 'CG_StraightSkeleton', ST_AsText(CG_StraightSkeleton('POLYGON((1 1,2 1,2 2,1 2,1 1))'));
+-- #4323: both skeleton operations ignore an input Z dimension.
+SELECT 'CG_StraightSkeletonDropsZ', ST_NDims(CG_StraightSkeleton('POLYGON Z((0 0 10,0 50 10,10 50 10,10 0 10,0 0 10))'));
+SELECT 'CG_ApproximateMedialAxisDropsZ', ST_NDims(CG_ApproximateMedialAxis('POLYGON Z((0 0 10,0 50 10,10 50 10,10 0 10,0 0 10))'));
SELECT 'CG_StraightSkeletonUseMDistance',
CASE WHEN string_to_array(postgis_sfcgal_version(), '.')::int[] >= string_to_array('1.3.8', '.')::int[]
THEN
diff --git a/sfcgal/regress/regress_sfcgal_expected b/sfcgal/regress/regress_sfcgal_expected
index d5c3005a2f..ea9616bb20 100644
--- a/sfcgal/regress/regress_sfcgal_expected
+++ b/sfcgal/regress/regress_sfcgal_expected
@@ -23,6 +23,8 @@ CG_3DConvexHull|80.9227
CG_3DUnion|t
CG_3DUnion (aggregate)|t
CG_StraightSkeleton|MULTILINESTRING((1 1,1.5 1.5),(2 1,1.5 1.5),(2 2,1.5 1.5),(1 2,1.5 1.5))
+CG_StraightSkeletonDropsZ|2
+CG_ApproximateMedialAxisDropsZ|2
CG_StraightSkeletonUseMDistance|MULTILINESTRING M ((0 0 0,0.5 0.5 0.5),(1 0 0,0.5 0.5 0.5),(1 1 0,0.5 0.5 0.5),(0 1 0,0.5 0.5 0.5))
CG_Distance|5
CG_3DDistance|1
-----------------------------------------------------------------------
Summary of changes:
NEWS | 2 ++
doc/reference_sfcgal.xml | 3 ++-
doc/reference_sfcgal_legacy.xml | 6 ++++++
sfcgal/regress/regress_sfcgal.sql | 3 +++
sfcgal/regress/regress_sfcgal_expected | 2 ++
5 files changed, 15 insertions(+), 1 deletion(-)
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