Thank you @spikeyxxx. I checked … but unfortunately that doesn’t seem to be the problem. The cube has dimensions of 240x240x50 meters, the scale was not applied.
I append a screenshot *before* I connect the gradient with the fog filling all the cube, and one just *after* I connect it. Nothing changes, but the fog completelydisappears.
(*Edit* Unfortunately I don’t manage to upload the pictures.)
