ST_3DConvexHull
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## Name

ST_3DConvexHull — Computes the 3D convex hull of a geometry.

## Synopsis

`geometry ST_3DConvexHull(`geometry geom1`)`;

## Description

Availability: 3.3.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsText(ST_3DConvexHull('LINESTRING Z(0 0 5, 1 5 3, 5 7 6, 9 5 3 , 5 7 5, 6 3 5)'::geometry));

    POLYHEDRALSURFACE Z (((1 5 3,9 5 3,0 0 5,1 5 3)),((1 5 3,0 0 5,5 7 6,1 5 3)),((5 7 6,5 7 5,1 5 3,5 7 6)),((0 0 5,6 3 5,5 7 6,0 0 5)),((6 3 5,9 5 3,5 7 6,6 3 5)),((0 0 5,9 5 3,6 3 5,0 0 5)),((9 5 3,5 7 5,5 7 6,9 5 3)),((1 5 3,5 7 5,9 5 3,1 5 3)))

    WITH f AS (SELECT i, ST_Extrude(geom, 0,0, i ) AS geom
    FROM ST_Subdivide(ST_Letters('CH'),5) WITH ORDINALITY AS sd(geom,i)
          )
          SELECT ST_3DConvexHull(ST_Collect(f.geom) )
          FROM f;

Original geometry overlaid with 3D convex hull

## See Also

ST_Letters, ST_AsX3D

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