millman, Your glider flight reminded me of something interesting. I live in the italian alps, about 6,000 feet up, in the middle of nowhere. About 10 days ago, I stepped out onto the balcony sometime after midnight, It was bright moonlight, and I saw that a bank of fog (read 'cloud' up where I am) had moved up the valley. The peculiar thing about it was that the top of the fog was perfectly flat - like it had been sliced with a knife - and the moon was shining down on it. The cloud was thin enough for me to see the landscape below through it, but the whole thing looked too weird. It was more like water, than cloud. I've actually seen something similar several times before here. What look like flat lakes of fog across the valley. Anyway, the point is, I thought to myself at the time "If I were to render a scene like that, no one would ever consider it realistic". I've seen some incredible weather phenomena that, if you saw them in a 3d scene,you'd say "No way!" So, sometimes reality just isn't believable enough for us. Or too unbelievable, maybe. mac