The Godrays are also planes with images on them, albeit done very well. I think DS may need a few more updates (and maybe Iray as well) before we get true volumetrics in DS. Having said that, you MIGHT be able to get them now (I'm just not sure if DS supports it) if you can make a shader in MDL and get it into DS. MDL is the shader language that Iray uses. I know there are some nodes in the Shader Mixer for MDL, I'm just not certain if any volumetric materials can be made with them at the current time.

Laurie