ST_Extrude (in PostGIS) of M geometries looses M

[robe2]

I think the issue we have ticketed at https://trac.osgeo.org/postgis/ticket/2756 is an SFCGAL issue.
So switched milestone to SFCGAL. Let me know if this can be fixed or not. I can mark it as a no-fix and just put a warning in docs. It's a rare use I think anyway.

SELECT ST_AsText(ST_Extrude('LINESTRING M (-10 50 1,50 -10 1)'::geometry, 20.1,20.1,20.1) );

Gives:

POLYHEDRALSURFACE Z (((-10 50 0,50 -10 0,70.1 10.1 20.1,10.1 70.1 20.1,-10 50 0)))

[mhugo]

There is no common rule of what is expected when creating a new M (copy it ? multiply it by the length of the extrusion vector ?). So we drop it. It should be documented this way indeed :)

[danielcu888]

@mhugo I don't mind doing this if you wish to assign it to me.

[danielcu888]

Thanks, @lbartoletti I'll get started on this today.

[danielcu888]

@lbartoletti I have submitted PR 228 to address this issue.

[danielcu888]

@lbartoletti this can now be resolved I think.