This week I experimented with God Rays. I used Pxrvolume and Pxrvolumebox but sticked with box. However I ran into a problem where other lights that are in the box won't render. I was hoping Nuke might fix this when I render lights individually, but I have yet to try this.
PS: image of God ray, but exposure was very low without other lights and the pxrvolumebox seems to make the lights very dim.