ST_3DLongestLine
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## Name

ST_3DLongestLine — Returns the 3D longest line between two geometries

## Synopsis

`geometry ST_3DLongestLine(`geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional longest line between two geometries. The function returns the first longest line if more than one. The line returned starts in g1 and ends in g2. The 3D length of the line is equal to the distance returned by ST_3DMaxDistance.

Availability: 2.0.0

Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

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

This function supports Polyhedral surfaces.

## Examples

linestring and point -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

               lol3d_line_pt           |       lol2d_line_pt
    -----------------------------------+----------------------------
     LINESTRING(50 75 1000,100 100 30) | LINESTRING(98 190,100 100)
linestring and multipoint -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

              lol3d_line_pt          |      lol2d_line_pt
    ---------------------------------+--------------------------
     LINESTRING(98 190 1,50 74 1000) | LINESTRING(98 190,50 74)
MultiLineString and Polygon both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(poly, mline)) As lol3d,
        ST_AsEWKT(ST_LongestLine(poly, mline)) As lol2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                lol3d             |          lol2d
    ------------------------------+--------------------------
     LINESTRING(175 150 5,1 10 2) | LINESTRING(175 150,1 10)

## See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_3DShortestLine, ST_3DMaxDistance

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