> On desert you can see images in the air. You know how ?> http://www.islandnet.com/~see/weather/graphics/photos/supmirag.gif
On hot roads too, you know...
It's an ior gradient.
You can easily reproduce this phnomenon in pov... and get max_trace_level
very high. (you put boxes with progressive ior and check the result).
selsek
