2D Surroundings do not receive any shadows

Solution

To properly render shadows Stellar needs a shadow receiving geometry but 2D surroundings are not considered as geometric objects.

Workaround:

• Create a shadow catcher geometry (e.g. a Plane object).
• Select the shell of your shadow catcher geometry.
• In the Object editor -> Illumination tab activate Use object as shadow catcher (see picture).
• Assign a Matte material to the shadow catcher geometry.

See also How to set up a Local surrounding as visible environment with AO ground shadow.