Created attachment 159571 [details]
Examples of 3D objects for testing specularity
Open attached document. It has
a 3D-object made by extrusion, shown with visible front face, top face and back face
a 3D-object made by rotation, angle 180°, so that front face and back face are visible
a 3D cube
Notice, that front and back faces do not show the specular light.
The problem is not, that front and back faces are plane. The cube has plane faces too and the side faces of the extrusion objects are plane too.
Confirmed, already with 4.4.7 and 3.3.0 (those on Win 10).
Arch Linux 64-bit
Build ID: bb64b19e3e8942e610db2d3596d859f7c7864811
CPU threads: 8; OS: Linux 5.8; UI render: default; VCL: kf5
Locale: fi-FI (fi_FI.UTF-8); UI: en-US
Built on 5 September 2020