Particular question.

We have a project coming up that is going to need particles flowing around video layers in the After Effects 3D Space. I've downloaded the demo of Particular (wonderful product BTW). After setting up a rudimentary light emitter moving around a solid I've placed in a 3D space composition, the solid does not hide the particles emitted "behind" it. Is there a way around this? Can someone point me to a tutorial that does something like this? Any help would be great.