This week's photo topic from Chris Marquardt is shooting with volumetric light. Light can have volume to it, as it lights up a space, especially if the light crosses dust, mist, fog, or smoke. That's how sunbeams are shown. They give the light shape, volume, and color. You'll also see fog being used at concerts at shows so that it can give light shape for more dramatic lighting schemes. Your lens can also give light its shape due to lens flare or reflections. Also called lens bloom. If you shoot in film, there's a specific film called Aura film that can cause it. Long exposure can also highlight the volume of light. That's what light painting does.
Here are some photos: