in samples\objects\volumes_01, I try to set one of the spheres to get big enough (I need about R=7000). But when the size reaches about R=1500, the fog starts to disappear, depending on distance from camera.
I tried ObjectVolumeBox instead of ObjectVolumeSphere, - the box works fine. The sphere with volume_light_base material also works fine at big sizes. But I need a big fog sphere.