Box3D always gets cast to 2D geometry

[robe]

Actually not sure if this is solvable. But ST_SetSRID, ST_Force_3DZ all lose the Z coordinate value of a BOX3D.

Example:

SELECT ST_AsEWKT(ST_Force_3DZ(ST_Extent3D(foo.the_geom))) As b3extentpoly, ST_Extent3D(foo.the_geom) As b3extent FROM (SELECT ST_MakePoint(x,y,z) As the_geom

FROM generate_series(1,3) As x

CROSS JOIN generate_series(1,2) As y CROSS JOIN generate_series(0,2) As Z) As foo;

Yields: b3extentpoly b3extent POLYGON((1 1 0,1 2 0,3 2 0,3 1 0,1 1 0)) ;BOX3D(1 1 0,3 2 2)

I would expect the POLYGON value to have some 2 z coords in there.

[mcayland]

The issue here is that the cast from BOX3D to geometry only works in 2 dimensions. Unfortunately the behaviour of the 3rd dimension is not really defined when casting from a cube, so we could interpolate the Z coordinates but at the end of the day that doesn't really help you at all.

Since there is no well-defined behaviour, we may as well stick with the 2D conversion with the Z coordinate set to 0 and mark this as 'Won't fix'.

ATB,

Mark.

[strk]

Wait a sec, box3d is not a cube, is it ? It's defined by 2 points only, you can't define a cube like that.

I've hit this problem as well, while trying to get a 3d envelope of a 2.5d geom.