duh, i forgot to tell you the update. the update is.... above, i said the camera has to be in the cone, and the spot light has to be outside the picture frame for the black spot to appear. this is incorrect. the only requisite is that the camera be in the cone. i did try one of those 'figures in the laser light tunnel' scenes, with the volumetric cone pointing right at the camera (actually, i think i used the quad for that one.) made it a blue colour, turned on the dust, turned down the ambient everything and all... pointed the spot at the camera, and ugh! one big black circle, no cool volumetric stuff.