Point density doesn't render I am trying to make a shockwave effect in blender, but when I add a cube surrounding the particle system, and set up the material nodes as shown in the image, the particles still don't show.

Here is the .blend file:
Firstly, you've set the point density to use the defining object's vertices rather than a particle system. Click Particle System and select the particle system you want to use.
  

Secondly, make sure the emitter itself isn't rendered, by unchecking Emitter in the Render panel in the particle system.