Our advanced user friend, we could ask you: what is a volumetric rendering?
But Ok, let us try to answer what we know
“Volumetric rendering” is a very blurred/undefined term/definition imho, each one uses it as he wants. In any case it’s a “rendering something not polygons/geometry”. It can be a rendering of fog, smoke, clouds etc. Ofren “volumetruc rendering” is related with hair/fur or even with grass cause it’s clear long ago: they cannot be rendered well with phong shading + megatons of polygons.
We know nothing about 3d apps that implements volumetric rendering directly. Instead hosts(LW or Max for example) support a special class of plug-ins to create volumetric effects. So, “volumetric rendering” is just an advanced plug-ins/shaders API. The host’s support is pretty simple: a plug-in receives a segment of ray(input) and returns to host a some color and transparency (output). The host automatically adds this output to final render. For all other things (for example, where a cloud should be located etc.) the plug-in is responsible itself.
So, don’t have illusions that “volumetric support” is a huge improvement, it’s a support only