hi and thx a lot! I´ll try that in 3 days, when back home.

one thing you mentioned is the black color inside. alltho the whole thing is extruded and allready has thickness it doesn´t prevent the light to have effect on the outside. btw the lampshade was initially lit with a pointlight. what you see are just a bunch of spheres glowing. I did set the light up now with a spotlight, added a physical_light to its lightShader plus used a parti_volume for creating this sunbeam effect. I didn´t find any other solution with mental ray. found this tut on the net which was quite what I needed.

https://www.jhavna.net/main.php?page=scatter



again, thank you for your support. I´ll post updates later when I´ve tried your suggestions.