Sorry it took so long to answer (- more problems with my laptop - now it has to go away for repairs, so still using husband's laptop.)

I tried a few things, and it turns out that the lines were caused by the edges of the lamp glass - turning off "cast shadows" for that material cured that problem.

I do already have a fairly high ambience on the bulb and filament - didn't try additive, I'll try that and increasing the ambience too...  Thanks for the suggestion.

Measure your mind's height
by the shade it casts.
Robert Browning (Paracelsus)

Fran's Freestuff

http://franontheedge.blogspot.com/

http://www.FranOnTheEdge.com