I've installed QGIS 2.99 to test its new features, particularly the 3D viewer, when I try the following I only see a square, not a 3D cube.
In PostGIS I make a square and extrude it
-- make a square CREATE TABLE public.square1 ( id serial, geom geometry, CONSTRAINT square1_pkey PRIMARY KEY (id) ); INSERT INTO public.square1 (geom) SELECT ST_MakePolygon(ST_GeomFromText('LINESTRING (0 0, 0 100, 100 100, 100 0, 0 0)')) AS geom;
I add the following sql via the db manager and add as a layer.
SELECT ST_SetSRID(ST_Extrude(ST_Buffer(square1.geom, 0),0,0,10), 27700) AS geom FROM Square1
But I only see 2D geometry, no 3D geometry. I had to set a srid, QGIS would not allow no projection or ESPG:4326
I test the polyhedral for its volume, this is correct
ST_volume(ST_Extrude(ST_Buffer(square1.geom, 0),0,0,10) ) AS volume FROM Square1
Where have I gone wrong?