Here is a little video to show you haw to use this generator with volumetric light :
You can also use a any
3D Generator with the
Random Points to produce almost the same results (except that points will be scattered over a surface instead of a volume).
This also make possible to sample custom
3D File, which is not possible with Random points generator.
If you want to change the shape of this generator, you can select it either inside the
Element Tree directly inside it's parameters inside the
Parameters Editor. To change the shape (position / orientation / size) select it in the element tree (red arrow):
Here is an example of a Random point generator with a box shape:
Here is a little comparison between this generator set as sphere and a
Geosphere with a
Random Points Modifier over it.