volume caustics with mental ray...

[vaiora]

hello...i'm just testing the mental ray particule volume shader...the effect that i looking for is a volume caustics refracted by a glass objet...(we can see similar effect when sunray comes light a dusty room).so i built a scene ; setup shader light ect....and when come time to render...there's no volume caustics effect...until i set down the light intensity to 0...the volume caustics apear but the scene is black...i don't know if someone can understand what i'm talking about...but i upload the scene and my results...here also the tut that i'm following: http://www.motiondesign.biz/vol_start.html
if someone know where's the problem...

[papa]

Have you tried contacting MotionDesign? This isn't one of our tutorials and you might get the answer you need directly from the authors of that informaton. Please contact them for details about your settings.